Anatomy and physiology of pregnancy. Mathernal
and fetal nutrition.
LEARNING OBJECTIVES
*
Determine gravidity and parity using the fiveand four-digit systems.
*
Describe the various types of pregnancy tests.
*
Explain the expected maternal anatomic and physiologic adaptations to
pregnancy.
*
Differentiate among presumptive, probable, and positive signs of pregnancy.
*
Identify the maternal hormones produced during pregnancy, their target organs,
and their major effects on pregnancy.
*
Compare the characteristics of the abdomen, vulva, and cervix of the nullipara
and multipara.
*
Explain recommended maternal weight gain during pregnancy.
*
Compare the recommended level of intake of energy sources, protein, and key
vitamins and minerals during pregnancy and lactation.
*
Give examples of the food sources that provide the nutrients required for
optimal maternal nutrition during pregnancy and lactation.
*
Examine the role of nutrition supplements during pregnancy.
*
List five nutritional risk factors during pregnancy.
*
Compare the dietary needs of adolescent and mature pregnant women.
*
Give examples of cultural food patterns and possible dietary problems for two
ethnic groups or for two alternative eating patterns.
KEY
TERMS AND DEFINITIONS
ballottement
Diagnostic technique using palpation: a
floating fetus, when tapped or pushed, moves away and then returns to touch the
examiner's hand
Braxton
Hicks sign Mild, intermittent, painless uterine contractions
that occur during pregnancy; occur more frequently as pregnancy advances but do
not represent true labor; however, they should be distinguished from preterm
labor
carpal tunnel syndrome
Pressure on the median nerve at the point at which it goes through the carpal
tunnel of the wrist; causes soreness, tenderness, and weakness of the muscles
of the thumb
Chadwick
sign Violet color of vaginal mucous membrane that is
visible from approximately the fourth week of pregnancy; caused by increased
vascularity
chloasma
Increased pigmentation over bridge of nose and cheeks of pregnant women and
some women taking oral contraceptives; also known as "mask of
pregnancy"
colostrum
Fluid in the acini cells of the breasts present from early pregnancy into the
early postpartal period; rich in antibodies, which provide protection to the
breastfed newborn from many diseases; high in protein, which binds bilirubin;
and laxative acting, which speeds the elimination of meconium and helps loosen
mucus
diastasis recti abdominis
Separation of the two rectus muscles along the median line of the abdominal
wall; often seen in women with repeated childbirths or with a multiple
gestation (e.g., triplets)
epulis
Tumorlike benign lesion of the gingiva seen in pregnant women
funic souffle Soft,
muffled, blowing sound produced by blood rushing through the umbilical vessels
and synchronous with the fetal heart sounds
Goodell sign
Softening of the cervix, a probable sign of pregnancy, occurring during the
second month
Hegar sign
Softening of the lower uterine segment that is classified as a probable sign of
pregnancy, may be present during the second and third months of pregnancy, and
is palpated during bimanual examination
human chorionic gonadotropin (hCG)
Hormone that is produced by chorionic villi; the biologic marker in pregnancy
tests
leukorrhea
White or yellowish mucus discharge from the cervical canal or the vagina that
may be normal physiologically or caused by pathologic states of the vagina and
endocervix
lightening
Sensation of decreased abdominal distention produced by uterine descent into the
pelvic cavity as the fetal presenting part settles into the pelvis; usually
occurs 2 weeks before the onset of labor in nulliparas
linea nigra Line of
darker pigmentation seen in some women during the latter part of pregnancy that
appears on the middle of the abdomen and extends from the symphysis pubis
toward the umbilicus
operculum
Plug of mucus that fills the cervical canal during pregnancy
palmar erythema Rash on the
surface of the palms sometimes seen in pregnancy
ptyalism Excessive
salivation
pyrosis Burning
sensation in the epigastric and sternal region from stomach acid (heartburn)
quickening Maternal
perception of fetal movement; usually occurs between weeks 16 and 20 of
gestation
striae gravidarum "Stretch
marks"; shining reddish lines caused by stretching of the skin, often
found on the abdomen, thighs, and breasts during pregnancy; these streaks turn to a fine pinkish white or silver tone in
time in fair-skinned women and brownish in darker-skinned women
uterine
souffle Soft, blowing sound made by the blood in the arteries of the pregnant uterus
and synchronous with the maternal pulse
The goal of maternity
care is a healthy pregnancy with a physically safe and emotionally satisfying
outcome for mother, infant, and family. Consistent health supervision and
surveillance are of utmost importance in achieving this outcome. However, many
maternal adaptations are unfamiliar to pregnant women and their families.
Helping the pregnant woman recognize the relationship between her physical
status and the plan for her care assists her in making decisions and encourages
her to participate in her own care.
GRAVIDITY AND PARITY
An understanding of the
following terms used to describe pregnancy and the pregnant woman is essential
to the study of maternity care:
• Gravida—a woman who is pregnant
• Gravidity—pregnancy
• Multigravida—a woman who has had two or more pregnancies
• Multipara—a woman who has completed two or more pregnancies to the
stage of fetal viability
• Nulligravida—a woman who has never been pregnant
• Nullipara—a woman who has not completed a pregnancy with a fetus or
fetuses who have reached the stage of fetal viability
• Parity—the number of pregnancies in which the fetus or fetuses have
reached viability, not the number of fetuses (e.g., twins) born; whether the
fetus is born alive or is stillborn (fetus who shows no signs of life at birth)
after viability is reached does not affect parity
• Postdate or postterm—a pregnancy that goes beyond 42 weeks of
gestation
• Preterm—a pregnancy that has reached 20 weeks of gestation but
before completion of 37 weeks of gestation
• Primigravida—a woman who is pregnant for the first time
• Primipara—a woman who has completed one pregnancy with a fetus or
fetuses who have reached the stage of fetal viability
• Term—a pregnancy from the beginning of the thirtyeighth week of
gestation to the end of the forty-second week of gestation
• Viability—capacity to live outside the uterus; approximately 22 to
24 weeks since last menstrual period, or weight of fetus is greater than 500 g
Gravidity and parity
information is obtained during history-taking interviews and may be recorded in
patient records in several ways. One abbreviation commonly used in maternity
centers consists of five digits separated with hyphens. The first digit
represents the total number of pregnancies, including the present one (gravidity);
the second digit represents the total number of term births; the third
indicates the number of preterm births; the fourth identifies the number of
abortions (miscarriage or elective termination of pregnancy before viability);
and the fifth is the number of children currently living. The acronym GTPAL
(gravidity, term, preterm, abortions, living children)
may be helpful in remembering this system of notation. For example, if a woman
pregnant only once with twins gives birth at the thirty-fifth week and the
babies survive, the abbreviation that represents this information is
"1-0-1-0-2." During her next pregnancy the abbreviation is
"2-0-1-0-2." Additional examples are given in Table 1.
Others prefer a
four-digit system. The first digit of the five-digit system, which signifies
gravidity, is dropped. The acronym TPAL may be useful in remembering what the
four digits stand for.
|
Table 1 Gravidity and
Parity Using Five-Digit (GTPAL) System |
|||||
|
|
GRAVIDITY PREGNANCIES |
TERM BIRTH |
PRETERM BIRTH |
ABORTIONS |
LIVING CHILDREN |
|
Sarah is pregnant for the
first time. |
1 |
0 |
0 |
0 |
0 |
|
She carries the pregnancy
to term, and the neonate survives. |
1 |
1 |
0 |
0 |
1 |
|
She is pregnant again. |
2 |
1 |
0 |
0 |
1 |
|
Her second pregnancy ends
in abortion. |
2 |
1 |
0 |
1 |
1 |
|
During her third
pregnancy, she gives birth to preterm twins. |
3 |
1 |
1 |
1 |
3 |
PREGNANCY TESTS
Early detection of
pregnancy allows for early initiation of care. Human chorionic gonadotropin
(hCG) is the biologic marker on which pregnancy
tests are based. Production of hCG begins as early as the day of implantation
and can be detected in the blood as early as 6 days after conception, or
approximately 20 days since the last menstrual period (LMP), and in urine
approximately 26 days after conception (Cunningham et al., 2001). The level of hCG rises until it peaks at approximately 60 to 70 days of
gestation and then begins to decline. The lowest level is reached between 100
and 130 days of pregnancy and remains constant until birth (Varney, 1997).
Serum and urine
pregnancy tests are performed in clinics, offices, women's health centers, and
laboratory settings. Both serum and urine tests provide accurate results. A 7-
to 10-ml sample of venous blood is collected for serum testing. Most urine
tests require a first-voided morning urine specimen because it contains levels
of hCG approximately the same as those in serum.
Random urine samples usually have lower levels. Urine tests are less expensive
and provide more immediate results than serum tests (Hatcher et al., 1998).
Many different
pregnancy tests are available, but they all depend on recognition of hCG or a beta subunit of hCG. The wide variety of tests
precludes discussion of each; however, several categories of tests are
described here. The nurse should read the manufacturer's directions for the
test to be used.
Immunoassoys, or agglutination inhibition tests, depend on an antigen-antibody
reaction between hCG and an antiserum. Usually, the
antiserum is mixed with urine, and hCG-coated particles (e.g., latex or blood
cells) are added. If hCG is present in the urine,
agglutination does not occur because the hCG neutralizes the hCG antibody, and the
test is considered positive (Cunningham et al., 2001). Although immunologic
tests are accurate from 4 to 10 days after a missed period, they are most
appropriate for confirming a pregnancy at or after the sixth week of gestation (Hatcher
et al., 1998).
Radioimmunoassay
pregnancy tests for the beta subunit of hCG in serum
or urine samples use radioactively labeled markers and are usually performed in
a laboratory. These tests are accurate with low hCG
levels and can confirm pregnancy 1 week after conception (Hatcher et al.,
1998).
Radioreceptor assay is
a serum test that measures the ability of a blood sample to inhibit the binding
of radiolabeled hCG to receptors. The test is 90% to
95% accurate from 6 to 10 days after conception (Pagana & Pagana, 2001).
Enzyme-linked
immunosorbent assay (ELISA) testing is the most popular method of testing for
pregnancy. It uses a specific monoclonal antibody (anti-hCG) with enzymes to
bond with hCG in urine. Depending on the specific test,
levels of hCG as low as 5 to 50 mlU/ml can be detected
as early as 4 days after implantation (Hatcher et al., 1998). As an office or
home procedure it requires minimal time and offers results in 5 minutes. A
positive test is indicated by a simple color-change reaction.
ELISA technology is the
basis for most over-thecounter home pregnancy tests. With these one-step tests,
the woman usually applies urine to a strip and reads the results. The test kits
come with directions for collection of the specimen, the testing procedure, and
reading of the results. Most manufacturers of the kits provide a toll-free telephone
number to call if users have concerns and questions about test procedures or
results (see Teaching Guidelines box). The most common error in performing home
pregnancy tests is doing the test too early in pregnancy (Hatcher et al.,
1998).
|
TEACHING GUIDELINES Home Pregnancy Testing • Follow the manufacturer's instructions carefully. Do not omit steps. • Review the manufacturer's list of foods, medications, and other
substances that can affect the test results. • Use a first-voided morning urine specimen. • If the test done at the time of your missed period is negative,
repeat the test in 1 week if you still have not had a period. • If you have questions about the test, contact the manufacturer. • Contact your health care provider for follow-up
if the test is positive or if the test is negative and you still have not had
a period |
Interpreting the results
of pregnancy tests requires some judgment. The type of pregnancy test and its
degree of sensitivity (ability to detect low levels of a substance) and specificity
(ability to discern the absence of a substance) have to be considered in
conjunction with the woman's history. This includes the date of her last normal
menstrual period (LNMP), her usual cycle length, and results of previous pregnancy
tests. It is important to know if the woman is a substance abuser and what
medications she is taking, because medications such as anticonvulsants and tranquilizers
can cause false-positive results and diuretics and promethazine can cause
false-negative results (Pagana & Pagana, 2001). Improper collection of the
specimen, hormone-producing tumors, and laboratory errors also may cause false
results. Whenever there is any question, further evaluation or retesting may be
appropriate.
ADAPTATIONS TO PREGNANCY
Maternal physiologic
adaptations are attributed to the hormones of pregnancy and to mechanical
pressures arising from the enlarging uterus and other tissues. These
adaptations protect the woman's normal physiologic functioning, meet the
metabolic demands pregnancy imposes on her body, and provide a nurturing
environment for fetal development and growth. Although pregnancy is a normal phenomenon,
problems can occur.
SIGNS OF PREGNANCY
Some of the physiologic
adaptations are recognized as signs and symptoms of pregnancy. Three commonly
used categories ofsigns and symptoms of pregnancy are presumptive, those changes
felt by the woman (e.g., amenorrhea, fatigue, nausea and vomiting, breast
changes);probable, those changes observed by an
examiner (e.g., Hegar sign, ballottement, pregnancy tests); and positive, those
signs that are attributed only to the presence of the fetus (e.g., hearing fetal
heart tones, visualization of the fetus, and palpating fetal movements). Table
2 summarizes the signs of pregnancy in relation to when they might occur and
other causes for their occurrence.
|
Table 2 Sign and Pregnancy |
||
|
TIME OF OCCURRENCE (GESTATIONAL
AGE) |
SIGN |
OTHER POSSIBLE CAUSE |
|
PRESUMPTIVE SIGNS |
||
|
3-4 wk |
Breast changes |
Premenstrual changes, oral contraceptives |
|
4 wk |
Amenorrhea |
Stress,
vigorous exercise, early menopause, endocrine problems, malnutrition |
|
4-14 wk |
Nausea, vomiting |
Gastrointestinal virus, food poisoning |
|
6-12 wk |
Urinary frequency |
Infection, pelvic tumors |
|
12 wk |
Fatigue |
Stress, illness |
|
16-20 wk |
Quickening |
Gas, peristalsis |
|
PROBABLE SIGNS |
||
|
5 wk |
Goodell sign |
Pelvic congestion |
|
6-8 wk |
Chadwick sign |
Pelvic congestion |
|
6-12 wk |
Hegar sign |
Pelvic congestion |
|
4-12 wk |
Positive pregnancy test (serum) |
Hydatidiform mole, choriocarcinoma |
|
6-12 wk |
Positive result to pregnancy test
(urine) |
False-positive results may be
caused by pelvic infection, tumors |
|
16 wk |
Braxton Hicks contractions |
Myomas, other tumors |
|
16-28 wk |
Ballottement |
Tumors, cervical polyps |
|
POSITIVE SIGNS |
||
|
5-6 wk |
Visualization of fetus by real-time ultrasound examination |
No other causes |
|
16wk |
Visualization of fetus by x-ray
study |
|
|
6 wk |
Fetal heart tones detected by
ultrasound examination |
|
|
8-17 wk |
Fetal heart tones detected by
Doppler ultrasound stethoscope |
|
|
17-19 wk |
Fetal heart tones detected by fetal
Stethoscope |
|
|
19-22 wk |
Fetal movements palpated |
|
|
Late pregnancy |
Fetal movements visible |
|
REPRODUCTIVE SYSTEM AND
BREASTS
Uterus
The phenomenal uterine
growth in the first trimester is stimulated by high levels of estrogen and
progesterone. Early uterine enlargement results from increased vascularity and
dilation of blood vessels, hyperplasia (production of new muscle fibers and
fibroelastic tissue) and hypertrophy (enlargement of preexisting muscle fibers
and fibroelastic tissue), and development of the decidua. By 7 weeks of
gestation, the uterus is the size of a large hen's egg; by 10 weeks of
gestation, it is the size of an orange (twice its nonpregnant size); and by 12
weeks of gestation, it is the size of a grapefruit. After the third month,
uterine enlargement is primarily the result of mechanical pressure of the
growing fetus (Varney, 1997).
As the uterus enlarges,
it also changes in shape and position. At conception the uterus is shaped like
an upsidedown pear. During the second trimester, as the muscular walls
strengthen and become more elastic, the uterus becomes spherical or globular.
Later, as the fetus lengthens, the uterus becomes larger and more ovoid and
rises out of the pelvis into the abdominal cavity.
The pregnancy may
"show" after the fourteenth week, although this depends to some
degree on the woman's height and weight. Abdominal enlargement may be less apparent
in the nulipara with good abdominal muscle tone (Fig. 1). Posture also
influences the type and degree of abdominal enlargement that occurs. In normal
pregnancies the uterus enlarges at a predictable rate. As the uterus grows, it
may be palpated above the symphysis pubis some time between the twelfth and
fourteenth weeks of pregnancy (Fig. 2). The uterus rises gradually to the level
of the umbilicus at 22 to 24 weeks of gestation and nearly reaches the xiphoid
process at term. Between weeks 38 and 40, fundal height drops as the fetus
begins to descend and engage in the pelvis (lightening) (Fig. 2, dashed
line). Generally, lightening occurs in the nullipara approximately 2 weeks
before the onset of labor and at the start of labor in the multipara.
Fig. 1 Comparison of
abdomen, vulva, and cervix in nullipara
(A)
and multipara (B) at the same stage of pregnancy.
Fig.
2 Height of fundus by weeks of normal gestation with a single fetus. Dashed line indicates height after lightening. (From Seidel, H. et al. [1999]. Mosby's guide to physical examination
[4th ed.].
Uterine enlargement is
determined by measuring fundal height, a measurement commonly used to estimate
the duration of pregnancy. However, variation in the position of the fundus or
the fetus, variations in the amount of amniotic fluid present, the presence of
more than one fetus, maternal obesity, and variation in examiner techniques can
reduce the accuracy of this estimation of the duration of pregnancy.
The uterus normally
rotates to the right as it elevates, probably because of the presence of the
rectosigmoid colon on the left side. However, the extensive hypertrophy (enlargement)
of the round ligaments keeps the uterus in the midline. Eventually, the growing
uterus touches the anterior abdominal wall and displaces the intestines to
either side of the abdomen (Fig. 3). When a pregnant woman is standing, most of
her uterus rests against the anterior abdominal wall, and this contributes to
altering her center of gravity.
Fig.
3 Displacement of internal abdominal structures and diaphragm by the enlarging
uterus at 4, 6, and 9 months of gestation.
At approximately 6
weeks of gestation, softening and compressibility of the lower uterine segment
(the uterine isthmus) occur (Hegar sign). This results in exaggerated uterine
anteflexion during the first 3 months of pregnancy (Fig. 4). In this position
the uterine fundus presses on the urinary bladder, causing the woman to
experience urinary frequency.
Fig. 4 Hegar sign.
Bimanual examination for assessing compressibility, softening of isthmus (lower
uterine segment) while the cervix is still firm.
Early uterine
enlargement may not be symmetric, depending on the site of implantation. For
example, if corneal implantation occurred, a soft, irregular bulge (Piskacek sign)
may be detected during a pelvic examination (Varney, 1997).
Changes in
contractility. Soon after the fourth month of pregnancy, uterine
contractions can be felt through the abdominal wall. These contractions are
referred to as the Braxton Hicks sign. Braxton Hicks contractions are
irregular, painless contractions that occur intermittently throughout
pregnancy. These contractions facilitate uterine blood flow through the
intervillous spaces of the placenta and thereby promote oxygen delivery to the
fetus. Although Braxton Hicks contractions are not painful, some women do
complain that they are annoying. After the twenty-eighth week, these
contractions become much more definite, but they usually cease with walking or
exercise. Braxton Hicks contractions can be mistaken for preterm and true
labor; however, they do not increase in intensity or frequency or cause
cervical dilation.
Uteroplacental
blood flow. Placental perfusion depends on the maternal blood
flow to the uterus. Blood flow increases rapidly as the uterus increases in
size. Although uterine blood flow increases twentyfold, the fetoplacental unit
grows more rapidly. Consequently, more oxygen is extracted from the uterine
blood during the latter part of pregnancy (Cunningham et al., 2001). In a
normal term pregnancy, one sixth of the total maternal blood volume is within
the uterine vascular system. The rate of blood flow through the uterus averages
500 ml/min, and oxygen consumption of the gravid uterus increases to meet fetal
needs. A low maternal arterial pressure, contractions of the uterus, and
maternal supine position are three factors known to decrease blood flow.
Estrogen stimulation may increase uterine blood flow. Doppler ultrasound can be
used to measure uterine blood flow velocity, especially in pregnancies at risk because
of conditions associated with decreased placental perfusion such as
hypertension, intrauterine growth restriction, diabetes mellitus, and multiple gestation (Creasy & Resnik, 1999). Using an ultrasound
device or a fetal stethoscope, the health care provider may hear the uterine
soufflé or the funic souffle.
Cervical
changes. A softening of the cervical tip called Goodell sign
may be observed at approximately the beginning of the sixth week in a normal,
unscarred cervix. This sign is brought about by increased vascularity, slight hypertrophy,
and hyperplasia (increase in number of cells) of the muscle and its
collagen-rich connective tissue, which becomes loose, edematous, highly
elastic, and increased in volume. The glands near the external os proliferate beneath
the stratified squamous epithelium, giving the cervix the velvety appearance
characteristic of pregnancy. Friability
is increased and may cause slight bleeding after coitus with deep penetration
or after vaginal examination. Pregnancy can also cause the squamocolumnar junction,
the site for obtaining cells for cervical cancer screening, to be located away
from the cervix. Because of all these changes, evaluation of abnormal
Papanicolaou tests during pregnancy can be complicated. However, careful assessment
of all pregnant women is important because approximately 3% of all cervical
cancers are diagnosed during pregnancy (Creasy & Resnik, 1999).
The cervix of the
nullipara is rounded. Lacerations of the cervix almost always occur during the
birth process. With or without lacerations, however, after childbirth the cervix
becomes more oval in the horizontal plane, and the external os appears as a
transverse slit (see Fig. 1).
Changes related to the presence of
the fetus. Passive movement of the
unengaged fetus is called ballottement and can be identified generally
between the sixteenth and eighteenth week. Ballottement is a technique of palpating
a floating structure by bouncing it gently and feeling it rebound. In the
technique used to palpate the fetus, the examiner places a finger in the vagina
and taps gently upward, causing the fetus to rise. The fetus then sinks, and a
gentle tap is felt on the finger (Fig. 5).
Fig.
5 Internal ballottement (18 weeks).
The first recognition
of fetal movements, or "feeling life," by the multiparous woman may
occur as early as the fourteenth to sixteenth week. The nulliparous woman may not
notice these sensations until the eighteenth week or later. Quickening
is commonly described as a flutter and is difficult to distinguish from
peristalsis. Gradually, fetal movements increase in intensity and frequency.
The week when quickening occurs provides a tentative clue in dating the
duration of gestation.
Vagina and vulva
Pregnancy hormones
prepare the vagina for stretching during labor and birth by causing the vaginal
mucosa to thicken, connective tissue to loosen, smooth muscle to hypertrophy, and
the vaginal vault to lengthen. Increased vascularity results in a violet-bluish
color of the vaginal mucosa and cervix. The deepened color, termed Chadwick sign,
may be evident as early as the sixth week, but is easily noted at the eighth
week of pregnancy (Creasy & Resnik, 1999).
Leukorrhea is a white or slightly gray mucoid discharge with a
faint musty odor. This copious mucoid fluid occurs in response to cervical
stimulation by estrogen and progesterone. The fluid is whitish because of the
presence of many exfoliated vaginal epithelial cells caused by hyperplasia of
normal pregnancy. This vaginal discharge is never pruritic or blood stained.
Because of the progesterone effect, ferning usually does not occur in the dried
cervical mucous smear, as it would in a smear of amniotic fluid. Instead, a beaded
or cellular crystallizing pattern formed in the dried mucus is seen (Cunningham
et al., 2001). The mucus fills the endocervical canal, resulting in the
formation of the mucous plug (operculum) (Fig. 6). The operculum acts as
a barrier against bacterial invasion during pregnancy
Fig.
6 A, Cervix in nonpregnant woman. B, Cervix during pregnancy.
During pregnancy, the
pH of vaginal secretions ranges from approximately 3.5 to 6. The increased
production of lactic acid in the vaginal epithelium, probably caused by increased
estrogen levels, produces a more acid environment. However, the pregnant woman
is more vulnerable to some vaginal infections, especially yeast infections (Bennett
& Brown, 1999).
The increased
vascularity of the vagina and other pelvic viscera results in a marked increase
in sensitivity. The increased sensitivity may lead to a high degree of sexual
interest and arousal, especially during the second trimester of pregnancy. The
increased congestion plus the relaxed walls of the blood vessels and the heavy
uterus may result in edema and varicosities of the vulva. The edema and varicosities
usually resolve during the postpartum period.
External structures of
the perineum are enlarged during pregnancy because of an increase in
vasculature, hypertrophy of the perineal body, and deposition of fat (Fig. 7). The
labia majora of the nullipara approximate and obscure the vaginal introitus;
those of the parous woman separate and gape after childbirth and perineal or
vaginal injury. Fig. 1 compares the perineum of the nullipara and the multipara
in relation to the pregnant abdomen, vulva, and cervix.
Fig.
7 A, Pelvic floor in nonpregnant woman. B, Pelvic floor at end of pregnancy. Note marked
hypertrophy and hyperplasia below dashed line joining tip of coccyx and
inferior margin of symphysis. Note elongation of bladder and urethra as a
result of compression. Fat deposits are increased.
Breasts
Fullness, heightened
sensitivity, tingling, and heaviness of the breasts begins
in the early weeks of gestation in response to increased levels of estrogen and
progesterone. Breast sensitivity varies from mild tingling to sharp pain. Nipples
and areolae become more pigmented; secondary pinkish areolae develop, extending
beyond the primary areolae; and nipples become more erectile. Hypertrophy of
the sebaceous (oil) glands embedded in the primary areolae, called
The richer blood supply
causes the vessels beneath the skin to dilate. Once barely noticeable, the
blood vessels become visible, often appearing in an intertwining blue network
beneath the surface of the skin. Venous congestion in the breasts is more
obvious in primigravidas. Striae gravidarum may appear at the outer aspects of
the breasts.
During the second and
third trimesters, growth of the mammary glands accounts for the progressive
breast enlargement. The high levels of luteal and placental hormones in
pregnancy promote proliferation of the lactiferous ducts and lobule-alveolar
tissue, so palpation of the breasts reveals a generalized, coarse nodularity.
Glandular tissue displaces connective tissue, and as a result the tissue becomes
softer and looser.
Although development of
the mammary glands is functionally complete by midpregnancy, lactation is
inhibited until a drop in estrogen level occurs after the birth. A thin, clear,
viscous secretory material (precolostrum) can be found in the acini cells by
the third month of gestation.
Colostrum, the creamy, white/yellowish to orange premilk fluid, may be expressed
from the nipples as early as 16 weeks of gestation (
GENERAL BODY SYSTEMS
Cardiovascular system
Maternal adjustments to
pregnancy involve extensive changes in the cardiovascular system, both anatomic
and physiologic. Cardiovascular adaptations protect the woman's normal
physiologic functioning, meet the metabolic demands pregnancy imposes on her
body, and provide for fetal developmental and growth needs.
Slight cardiac
hypertrophy (enlargement) is probably secondary to the increased blood volume
and cardiac output that occurs. The heart returns to its normal size after childbirth.
As the diaphragm is displaced upward by the enlarging uterus, the heart is
elevated upward and rotated forward to the left (Fig. 8). The apical impulse, a
point of maximum intensity, is shifted upward and laterally approximately 1 to
1.5 cm. The degree of shift depends on the duration of pregnancy and the size
and position of the uterus.
Fig. 8 Changes in
position of heart, lungs, and thoracic cage in pregnancy. Dashed
line, nonpregnant; solid line, change that occurs in pregnancy.
The changes in heart
size and position and increases in blood volume and cardiac output contribute
to auscultatory changes common in pregnancy. There is more audible splitting of
Sx and S2, and S, may be readily heard after 20 weeks of gestation. In
addition, systolic and diastolic murmurs may be heard over the pulmonic area. These
are transient and disappear shortly after the woman gives birth (Cunningham et
al., 2001).
Between 14 and 20 weeks
of gestation, the pulse increases approximately 10 to 15 beats per minute (beats/
min), which then persists to term. Palpitations may occur. In twin gestations,
the maternal heart rate increases significantly in the third trimester (Creasy
& Resnik, 1999).
The cardiac rhythm may
be disturbed. The pregnant woman may experience sinus arrhythmia, premature
atrial contractions, and premature ventricular systole. In the healthy woman
with no underlying heart disease, no therapy is needed; however, women with
preexisting heart disease will need close medical and obstetric supervision during
pregnancy.
Blood
pressure. Arterial blood pressure (brachial artery) is
affected by age, activity level, and presence of health problems. Additional
factors must be considered during pregnancy. These factors include maternal
anxiety, maternal position, and size and type of blood pressure apparatus.
Maternal anxiety can
elevate readings. If an elevated reading is found, the woman is given time to
rest, and the reading is repeated.
Maternal position
affects readings. Brachial blood pressure is highest when the woman is sitting,
lowest when she is lying in the lateral recumbent position, and intermediate when
she is supine, except for some women who experience supine hypotensive syndrome
(see following discussion). Therefore, at each prenatal visit, the reading
should be obtained in the same arm and with the woman in the same position. The
position and arm used should be recorded along with the reading.
The proper size cuff is
absolutely necessary for accurate readings. The cuff should be 20% wider than
the diameter of the arm around which it is wrapped, or approximately 12 to 14
cm for average-sized individuals and 18 to 20 cm for obese persons. Too small a
cuff yields a false-high reading; too large a cuff yields a false-low reading.
Caution should also be used when comparing auscultatory and oscillatory blood
pressure readings because discrepancies can occur (Green & Froman, 1996).
In the first trimester,
blood pressure usually remains the same as the prepregnancy level. During the
second trimester, there is a decrease in both systolic and diastolic pressure
of 5 to 10 mm Hg. This decrease is probably the result of peripheral vasodilation
caused by hormonal changes that occur during pregnancy. During the third
trimester, maternal blood pressure should return to the first-trimester levels.
Calculating the mean arterial pressure (MAP) (mean of the blood pressure in the
arterial circulation) can increase the diagnostic value of the findings. Normal
MAP readings in the nonpregnant woman are 86.4 ± 7.5 mm Hg. MAP readings for a
pregnant woman are slightly higher (Creasy 6 Resnik, 1999). One way to
calculate MAP is illustrated in
|
|
Some degree of
compression of the vena cava occurs in all women who lie flat on their backs
during the second half of pregnancy . Some women
experience a fall in their systolic blood pressure of more than 30 mm Hg. After
4 to 5 minutes a reflex bradycardia is noted, cardiac output is reduced by
half, and the woman feels faint. This condition is termed supine hypotensive syndrome (Cunningham et al., 2001).
Compression of the
iliac veins and inferior vena cava by the uterus causes increased venous
pressure and reduced blood flow in the legs (except when the woman is in the
lateral position). These alterations contribute to the dependent edema,
varicose veins in the legs and vulva, and hemorrhoids that develop in the
latter part of term pregnancy (Fig. 9).
Fig.
9 Hemorrhoids. (Courtesy Marjorie Pyle, RNC, Lifecircle,
Blood volume
and composition. The degree of blood volume expansion varies
considerably. Blood volume increases by approximately 1500
ml, or 40% to 45% above nonpregnancy levels (Cunningham et al., 2001).
This increase consists of 1000 ml of plasma plus 450 ml of red blood cells
(RBCs). The blood volume starts to increase at approximately the tenth to
twelfth week, peaks at approximately the thirty-second to thirty-fourth week, then decreases slightly at the fortieth week. The increase
in volume of a multiple gestation is greater than that for a pregnancy with a
single fetus (Creasy & Resnik, 1999). Increased volume is a protective
mechanism. It is essential for meeting the blood volume needs of the
hypertrophied vascular system of the enlarged uterus, adequately hydrating fetal
and maternal tissues when the woman assumes an erect or a supine position, and
providing a fluid reserve to compensate for blood loss during birth and the
puerperium. Peripheral vasodilation maintains a normal blood pressure despite
the increased blood volume in pregnancy.
During pregnancy there
is an accelerated production of RBCs (normal 4.2 to 5.4
million/mm3). The percentage of increase depends on the amount of iron
available. The RBC mass increases by approximately 17% (Creasy & Resnik,
1999).
Because the plasma
increase exceeds the increase in RBC production, there is a decrease in normal
hemoglobin values (12 to 16 g/dl blood) and hematocrit values (37% to 47%).
This state of hemodilution is referred to as physiologic anemia. The decrease is more noticeable during the
second trimester, when rapid expansion of blood volume takes place faster than
RBC production. If the hemoglobin value drops to 10 g/dl or less or if the
hematocrit drops to 35% or less, the woman is considered anemic.
The total white cell
count increases during the second trimester and peaks during the third
trimester. This increase is primarily in the granulocytes; the lymphocyte count
stays approximately the same throughout pregnancy. See Table 3 for laboratory
values during pregnancy.
|
Table
3 Laboratory values for Pregnant and Nonpregnant Women |
||
|
HEMATOLOGIC
VALUES Complete Blood Count (CBC) |
||
|
Hemoglobin (g/dl) |
12-16* |
>11* |
|
Hematocrit, packed cell volume (%) |
37-47 |
>33* |
|
Red blood cell (RBC) volume (per
ml) |
1600 |
1500-1900 |
|
Plasma volume (per ml) |
2400 |
3700 |
|
RBC count (million/mm3) |
4.2-5.4 |
5-6.25 |
|
White blood cells (total per mm3) |
5000-10,000 |
5000-15,000 |
|
Neutophils (%) |
55-70 |
60-85 |
|
Lymphocytes (%) |
20-40 |
15-40 |
|
Erythrocyte sedimentation rate
(mm/hr) |
20 |
Elevated second and third
trimesters |
|
Mean corpuscular hemoglobin
concentration (MCHC) (g/dl packed RBCs) |
32-36 |
No change hemoglobin concentration |
|
Mean corpuscular hemoglobin (MCH)
(pg) |
27-31 |
No change per picogram (less than a
nanogram) |
|
Mean corpuscular volume (MCV)
(yu.m3) |
80-95 |
No change per cubic micrometer |
|
Blood Coagulation and
Fibrinolytic Activityt |
||
|
Factor |
65-140 |
Increase in pregnancy, return to
normal in early puerperium; factor VIII increases during and immediately
after birth |
|
Factor |
55-145 |
|
|
Factor |
60-140 |
|
|
Factor |
45-155 |
|
|
Factor |
65-135 |
Decrease in pregnancy |
|
Factor |
50-150 |
|
|
Prothrombin time (PT) (sec) |
11-12.5 |
Slight decrease in pregnancy |
|
Partial thromboplastin time (PTT)
(sec) |
60-70 |
Slight decrease in pregnancy, and
decreases further during second and third stages of labor (indicates clotting
at placental site) |
|
Bleeding time (min) |
1-9 (Ivy) |
No appreciable change |
|
Coagulation time (min) |
6-10 (Lee/White) |
No appreciable change |
|
Platelets (per mm3) |
150,000-400,000 |
No significant change until 3-5
days after birth and then a rapid increase (may predispose woman to
thrombosis) and gradual return to normal |
|
Fibrinolytic activity |
|
Decreases in pregnancy and then
abrupt return to normal (protection against thromboembolism) |
|
Fibrinogen (mg/dl) |
200-400 |
Increased levels late in pregnancy |
|
Mineral/Vitamin
Concentrations |
||
|
Vitamin B12, folic acid, ascorbic acid |
|
|
|
Serum proteins Total (g/dl) Albumin (g/dl) Globulin, total (g/dl) |
6.4-8.3 3.5-5.0 2.3-3.4 |
5.5-7.5 Slight increase 3-4 |
|
Blood glucose Fasting (mg/dl) 2-Hour postprandial (mg/dl) |
70-105 <140 |
Decreases <140 after a 100-g carbohydrate
meal is considerednormal |
|
Acid-Base
Values in Arterial Blood |
||
|
Po2 |
80-100 |
104-108 (increased) |
|
Pco2 |
35-45 |
27-32 (decreased) |
|
Sodium bicarbonate (HCO3) (mEq/L) |
21-28 |
18-31 (decreased) |
|
Blood |
7.35-7.45 |
7.40-7.45 (slightly increased —more alkaline) |
|
HEPATIC
VALUES |
||
|
Bilirubin total (mg/dl) |
Not more than 1 mg/dl |
Unchanged |
|
Serum cholesterol (mg/dl) |
120-200 |
Increases from 16-32 weeks of
pregnancy; remains at this level until after birth |
|
Serum alkaline phosphatase (U/L) |
30-120 |
Increases from week 12 of pregnancy
to 6 weeks after birth |
|
Serum albumin (g/dl) |
3.5-5 |
Slight increase |
|
RENAL VALUES |
||
|
Bladder capacity (ml) |
1300 |
1500 |
|
Renal plasma flow (RPF) (ml/min |
490-700 |
Increase by 25%-30% |
|
Glomerular filtration rate (GFR) (ml/min) |
88-128 |
Increase by 30%-50% |
|
Nonprotein nitrogen (NPN) (mg/dl) |
25-40 |
Decreases |
|
Blood urea nitrogen (BUN) (mg/dl) |
10-20 |
Decreases |
|
Serum creatinine (mg/dl) |
0.5-1.1 |
Decreases |
|
Serum uric acid (mg/dl) |
2.7-7.3 |
Decreases |
|
Urine glucose |
Negative |
Present in 20% of pregnant women |
|
Intravenous pyelogram (IVP) |
Normal |
Slight to moderate hydroureter and hydronephrosis;
right kidney larger than left kidney |
Cardiac
output. Cardiac output increases from 30% to 50% over the
nonpregnant rate by the thirty-second week of pregnancy; it declines to
approximately a 20% increase at 40 weeks of gestation. This elevated cardiac
output is largely a result of increased stroke volume and heart rateand occurs
in response to increased tissue demands for oxygen (Creasy & Resnik, 1999).
Cardiac output in late pregnancy is appreciably higher when the woman is in the
lateral recumbent position than when she is supine. In the supine position, the
large, heavy uterus often impedes venous return to the heart and affects blood
pressure. Cardiac output increases with any exertion, such as labor and birth.
(Table 4 summarizes cardiovascular changes in pregnancy.)
|
TABLE 4 Cardiovascular Changes in
Pregnancy |
|
|
Heart rate |
Increases 10-15 beats/min |
|
Blood
pressure |
Remains at prepregnancy levels in
first trimester Slight decrease in second trimester Returns to prepregnancy levels in
third trimester |
|
Blood volume |
Increases by 1500 ml or 40%-45%
above prepregnancy level |
|
Red blood cell mass |
Increases 17% |
|
Hemoglobin |
Decreases |
|
Hematocrit |
Decreases |
|
White blood cell count |
Increases in second and third
trimester |
|
Cardiac output |
Increases 30%-50% |
Circulation
and coagulation times. The
circulation time decreases slightly by week 32. It returns to near normal near
term. There is a greater tendency for blood to coagulate (clot) during
pregnancy because of increases in various clotting factors (factors VII, VIII,
IX, X, and fibrinogen). This, combined with the fact
that fibrinolytic activity (the splitting up or the dissolving of a clot) is
depressed during pregnancy and the postpartum period, provides a protective
function to decrease the chance of bleeding but also makes the woman more
vulnerable to thrombosis, especially after cesarean birth.
Respiratory system
Structural and
ventilatory adaptations occur during pregnancy to provide for maternal and
fetal needs. Maternal oxygen requirements increase in response to the
acceleration in the metabolic rate and the need to add to the tissue mass in
the uterus and breasts. In addition, the fetus requires oxygen and a way to
eliminate carbon dioxide.
Elevated levels of
estrogen cause the ligaments of the rib cage to relax, permitting increased
chest expansion (see Fig. 8). The transverse diameter of the thoracic cage
increases by approximately 2 cm, and the circumference increases by 6 cm
(Cunningham et al., 2001). The costal angle increases and the lower rib cage appears to flare out. The chest may not return to its
prepregnant state after birth (Seidel et al., 1999).
The diaphragm is
displaced by as much as 4 cm during pregnancy. As pregnancy advances, thoracic
(costal) breathing replaces abdominal breathing, and
it becomes less possible for the diaphragm to descend with inspiration. Thoracic
breathing is primarily accomplished by the diaphragm rather than by the costal
muscles (Creasy & Resnik, 1999).
The upper respiratory
tract becomes more vascular in response to elevated levels of estrogen. As the
capillaries become engorged, edema and hyperemia develop within the nose,
pharynx, larynx, trachea, and bronchi. This congestion within the tissues of
the respiratory tract gives rise to several conditions commonly seen during
pregnancy. These conditions include nasal and sinus stuffiness, epistaxis (nosebleed),
changes in the voice, and a marked inflammatory response that can develop into
a mild upper respiratory infection.
Increased vascularity
of the upper respiratory tract also can cause the tympanic membranes and
eustachian tubes to swell, giving rise to symptoms of impaired hearing,
earaches, or a sense of fullness in the ears.
Pulmonary
function. Respiratory changes in pregnancy are related to the
elevation of the diaphragm and chest wall changes (Creasy & Resnik, 1999).
Changes in the respiratory center result in a lowered threshold for carbon dioxide.
The actions of progesterone and estrogen are presumed responsible for the
increased sensitivity of the respiratory center to carbon dioxide. In addition,
pregnant women become more aware of the need to breathe; some may even complain
of dyspnea at rest. (See Table 5 for respiratory changes in pregnancy.)
|
Table 5 Respiratory Changes in Pregnancy |
|
|
Respiratory rate |
Unchanged or slightly
increased |
|
Tidal volume |
Increased 30%-40% |
|
Vital capacity |
Unchanged |
|
Inspiratory |
Increased |
|
Expiratory |
Decreased |
|
Total |
Unchanged to slightly
decreased |
|
Oxygen consumption |
Increased 15%-20% |
Although pulmonary
function is not impaired by pregnancy, diseases of the respiratory tract may be
more serious during this time (Cunningham et al., 2001). One important factor
responsible for this may be the increased oxygen requirement.
Basal metabolism rate. The
basal metabolism rate (BMR) varies considerably in women at the beginning of and
during pregnancy, although it usually increases by 15% to 20% at term
(Worthington-Roberts & Williams, 1997). The BMR returns to nonpregnant
levels by 5 to 6 days postpartum. The elevation in BMR during pregnancy reflects
increased oxygen demands of the uterineplacental-fetal unit and greater oxygen
consumption because of increased maternal cardiac work (Chamberlain & Pipkin,
1998). Peripheral vasodilation and acceleration of sweat gland activity help
dissipate the excess heat resulting from the increased BMR during pregnancy.
Pregnant women may experience heat intolerance, which is annoying to some
women. Lassitude and fatigability after only slight exertion are experienced by
many women in early pregnancy. These feelings, along with a greater need for sleep,
may persist and may be caused in part by the increased metabolic activity.
Acid-base balance. Around
the tenth week of pregnancy, there is a decrease of approximately 5 mm Hg in the
partial pressure of carbon dioxide (PCO2). Progesterone may be responsible for
increasing the sensitivity of the respiratory center receptors so that tidal
volume is increased and PCO2 falls, the base excess (HCO3, or bicarbonate) falls,
and pH increases slightly. These alterations in acidbase balance indicate that
pregnancy is a state of respiratory alkalosis compensated by mild metabolic
acidosis (Chamberlain & Pipkin, 1998). These changes also facilitate the
transport of CO2 from the fetus and O2 release from the mother to the fetus
(see Table 3).
Renal system
The
kidneys are responsible for maintaining electrolyte and acid-base balance,
regulating extracellular fluid volume, excreting waste products, and conserving
essential nutrients.
Anatomic changes. Changes in renal structure during pregnancy result
from hormonal activity (estrogen and progesterone), pressure from an enlarging
uterus, and an increase in blood volume. As early as
the tenth week of pregnancy, the renal pelves and the ureters dilate. Dilation of
the ureters is more pronounced above the pelvic brim, in part because they are
compressed between the uterus and the pelvic brim. In most women the ureters below
the pelvic brim are of normal size. The smooth muscle walls of the ureters
undergo hyperplasia and hypertrophy and muscle tone relaxation. The ureters
elongate, become tortuous, and form single or double curves. In the latter part
of pregnancy, the renal pelvis and ureter are dilated more on the right side
than on the left because the heavy uterus is displaced to the right by the
sigmoid colon.
Because of
these changes, a larger volume of urine is held in the pelves and ureters, and
urine flow rate is slowed. The resulting urinary stasis or stagnation has the following
consequences:
•
There is a lag between the time urine is formed and when it reaches the
bladder. Therefore clearance test results may reflect substances contained in
glomerular filtrate several hours before.
•
Stagnated urine is an excellent medium for the growth of microorganisms. In
addition, the urine of pregnant women contains more nutrients, including
glucose, thereby increasing the pH (making the urine more alkaline). This makes
pregnant women more susceptible to urinary tract infection.
Bladder
irritability, nocturia, and urinary frequency and urgency (without dysuria) are
commonly reported in early pregnancy. Near term, bladder symptoms may return,
especially after lightening occurs.
Urinary
frequency results initially from increased bladder sensitivity and later from
compression of the bladder (see Fig. 7). In the second trimester the bladder is
pulled up out of the true pelvis into the abdomen. The urethra lengthens to 7.5
cm as the bladder is displaced upward. The pelvic congestion that occurs in
pregnancy is reflected in hyperemia of the bladder and urethra. This increased vascularity
causes the bladder mucosa to be traumatized and bleed easily. Bladder tone may
decrease, which increases the bladder capacity to 1500 ml. At the same time the
bladder is compressed by the enlarging uterus, resulting in the urge to void
even if the bladder contains only a small amount of urine.
Functional changes. In
normal pregnancy, renal function is altered considerably. Glomerular filtration
rate (GFR) and renal plasma flow increase early in pregnancy (Cunningham et
al., 2001). These changes are caused by pregnancy hormones, an increase in
blood volume, the woman's posture, physical activity, and nutritional intake. The
woman's kidneys must manage the increased metabolic and circulatory demands of
the maternal body and also excretion of fetal waste products. Renal function is
most efficient when the woman lies in the lateral recumbent position and least
efficient when the woman assumes a supine position. A side-lying position
increases renal perfusion, which increases urinary output and decreases edema.
When the pregnant woman is lying supine, the heavy uterus compresses the vena
cava and the aorta, and cardiac output decreases. As a result, blood flow to
the brain and heart is continued at the expense of other organs, including the
kidneys and uterus.
Fluid
and electrolyte balance. Selective renal tubular reabsorption
maintains sodium and water balance regardless of changes in dietary intake and
losses through sweat, vomitus, or diarrhea. From 500 to 900 mEq of sodium is normally
retained during pregnancy to meet fetal needs. To prevent excessive sodium depletion,
the maternal kidneys undergo a significant adaptation by increasing tubular reabsorption.
Because of the need for increased maternal intravascular and extracellular
fluid volume, additional sodium is needed to expand fluid volume and to
maintain an isotonic state. As efficient as the renal system is, it can be
overstressed by excessive dietary sodium intake or restriction or by use of
diuretics. Severe hypovolemia and reduced placental perfusion are two
consequences of using diuretics during pregnancy.
The
capacity of the kidneys to excrete water during the early weeks of pregnancy is
more efficient than later in pregnancy. As a result, some women feel thirsty in
early pregnancy because of the greater amount of water loss. The pooling of
fluid in the legs in the latter part of pregnancy decreases renal blood flow
and GFR. This pooling of blood in the lower legs is sometimes referred to as
physiologic edema or dependent edema and requires no treatment. The normal
diuretic response to the water load is triggered when the woman lies down,
preferably on her side, and the pooled fluid reenters general circulation.
Normally,
the kidney reabsorbs almost all of the glucose and other nutrients from the
plasma filtrate. In pregnant women, however, tubular reabsorption of glucose is
impaired so that glucosuria occurs at varying times and to varying degrees.
Normal values range from 0 to 20 mg/dl, meaning that during any one day the
urine is sometimes positive and sometimes negative. In nonpregnant women, blood
glucose levels must be at 160 to 180 mg/dl before glucose is
"spilled" into the urine (not reabsorbed). During pregnancy,
glycosuria occurs when maternal glucose levels are lower than 160 mg/dl. Why
glucose, as well as other nutrients such as amino acids, is wasted during
pregnancy is not understood, nor has the exact mechanism been discovered. Although
glycosuria may be found in normal pregnancies (2 + levels may be seen with
increased anxiety states), the possibility of diabetes mellitus and gestational
diabetes must be kept in mind.
Proteinuria
usually does not occur in normal pregnancy except during labor or after birth
(Cunningham et al., 2001). However, the increased amount of amino acids that must
be filtered may exceed the capacity of the renal tubules to absorb it, so small
amounts of protein are then lost in the urine. Values of trace to +1 protein
(dipstick assessment) or less than 300 mg/24 hr are acceptable during pregnancy
(Creasy & Resnik, 1999). The amount of protein excreted is not an
indication of the severity of renal disease, nor does an increase in protein
excretion in a pregnant woman with known renal disease necessarily indicate a
progression in her disease. However, a pregnant woman with hypertension and
proteinuria must be carefully evaluated because she may be at greater risk for
an adverse pregnancy outcome (see Table 3).
Integumentary system
Alterations
in hormonal balance and mechanical stretching are responsible for several
changes in the integumentary system during pregnancy. Hyperpigmentation is
stimulated by the anterior pituitary hormone melanotropin, which is increased
during pregnancy. Darkening of the nipples, areolae, axillae, and vulva occurs
at approximately the sixteenth week of gestation. Facial melasma, also called chloasma
or "mask of pregnancy," is a blotchy, brownish hyperpigmentation of
the skin over the cheeks, nose, and forehead, especially in dark-complexioned
pregnant women. Chloasma appears in 50% to 70% of pregnant women, beginning
after the sixteenth week and increasing gradually until term. The sun
intensifies this pigmentation in susceptible women. Chloasma caused by normal
pregnancy usually fades after birth.
The
linea nigra (Fig. 10) is a pigmented line extending from the symphysis
pubis to the top of the fundus in the midline; this line is known as the linea
alba before hormoneinduced pigmentation. In
primigravidas the extension of the linea nigra, beginning in the third month,
keeps pace with the rising height of the fundus; in multigravidas the entire line
often appears earlier than the third month. Not all pregnant women develop
linea nigra.
Fig.
10 Linea nigra. (From Seidel, H.
et al. [1999]. Mosby's guide to physical examination [4th ed.].
Striae
gravidarum, or stretch marks (seen over lower abdomen in Fig.
11), which appear in 50% to 90% of pregnant women during the second half of
pregnancy, may be caused by action of adrenocorticosteroids. Striae reflect
separation within the underlying connective (collagen) tissue of the skin. These
slightly depressed streaks tend to occur over areas of maximum stretch (i.e.,
abdomen, thighs, and breasts). The stretching sometimes causes a sensation that
resembles itching. The tendency to develop striae may be familial.
After birth they usually fade, although they never disappear completely. Color
of striae varies depending on the pregnant woman's skin color. The striae
appear pinkish on a woman with light skin and are lighter than surrounding skin
in dark-skinned women. In the multipara, in addition to the striae of the present
pregnancy, glistening silvery lines (in light-skinned women) or purplish lines
(in dark-skinned women) are commonly seen. These represent the scars of striae
from previous pregnancies.
Fig. 11 Striae gravidarum, or "stretch
marks." (Courtesy Michael S. Clement,
MD,
Angiomas
are commonly referred to as vascular spiders.They are tiny, star-shaped or
branched, slightly raised and pulsating end-arterioles usually found on the
neck, thorax, face, and arms. They occur as a result of elevated levels of circulating
estrogen. The spiders are bluish in color and do not blanch with pressure.
Vascular spiders appear during the second to the fifth month of pregnancy in
65% of Caucasian women and 10% of African-American women. The spiders usually
disappear after birth.
Pinkish
red, diffuse mottling or well-defined blotches are seen over the palmar
surfaces of the hands in approximately 60% of Caucasian women and 35% of
African-American women during pregnancy (Cunningham et al., 2001). These color
changes, called palmar erythema, are
related primarily to increased estrogen levels.
Pruritus
is a relatively common dermatologic symptom in pregnancy, with cholestasis of
pregnancy being the most common cause of pruritic rash. The goal of management
is to relieve the itching. Topical steroids are the usual treatment, although
systemic steroids may be needed. The problem usually resolves in the postpartum
period (Gordon & Landon, 1996).
Gum
hypertrophy may occur. An epulis
(gingival granuloma gravidarum) is a red, raised nodule on the gums that bleeds
easily. This lesion may develop around the third month and usually continues to
enlarge as pregnancy progresses. It is usually managed by avoiding trauma to
the gums (e.g., using a soft toothbrush). An epulis usually regresses spontaneously
after birth.
Nail
growth may be accelerated. Some women may notice thinning and softening of the
nails. Oily skin and acne vulgaris may occur during pregnancy. For some women the
skin clears and looks radiant. Hirsutism, the excessive growth of hair or
growth of hair in unusual places, is commonly reported. An increase in fine
hair growth may occur but tends to disappear after pregnancy. However, growth
of coarse or bristly hair does not usually disappear after pregnancy.
Increased
blood supply to the skin leads to increased perspiration. Women feel hotter
during pregnancy, possibly related to a progesterone-induced increase in body temperature
and the increased BMR.
Musculoskeletal system
The
gradually changing body and increasing weight of the pregnant woman cause
noticeable alterations in her posture (Fig. 12) and the way she walks. The
great abdominal distention that gives the pelvis a forward tilt, decreased
abdominal muscle tone, and increased weight bearing require a realignment of
the spinal curvature late in pregnancy. The woman's center of gravity shifts
forward. An increase in the normal lumbosacral curve (lordosis) develops, and a
compensatory curvature in the cervicodorsal region (exaggerated anterior
flexion of the head) develops to help her maintain her balance. Aching,
numbness, and weakness of the upper extremities may result. Large breasts and a
stoop-shouldered stance will further accentuate the lumbar and dorsal curves.
Walking is more difficult, and the waddling gait of the pregnant woman, called
"the proud walk of pregnancy" by Shakespeare, is well known. The
ligamentous and muscular structures of the middle and lower spine may be
severely stressed. These and related changes often cause musculoskeletal
discomfort, especially in older women or those with a back disorder or a faulty
sense of balance.
Fig.
12 Postural changes during pregnancy. A, Nonpregnant. B, Incorrect posture during pregnancy. C,
Correct posture during pregnancy.
Slight
relaxation and increased mobility of the pelvic joints are normal during
pregnancy. They are secondary to the exaggerated elasticity and softening of
connective and collagen tissue caused by increased circulating steroid sex hormones,
especially estrogen. Relaxin, an ovarian hormone, assists in this relaxation
and softening. These adaptations permit enlargement of pelvic dimensions to
facilitate labor and birth. The degree of relaxation varies, but considerable
separation of the symphysis pubis and the instability of the sacroiliac joints
may cause pain and difficulty in walking. Obesity and multifetal pregnancy tend
to increase the pelvic instability. Peripheral joint laxity also increases as
pregnancy progresses, but the cause is not known (Schauberger et al., 1996).
The
muscles of the abdominal wall stretch and ultimately lose some tone. During the
third trimester the rectus abdominis muscles may separate (Fig. 13), allowing abdominal
contents to protrude at the midline. The umbilicus flattens or protrudes. After
birth, the muscles gradually regain tone. However, separation of the muscles
(diastasis recti abdominis) may persist.
Fig.
13 Possible change in rectus abdominis muscles during pregnancy. A,
Neurologic system
Little
is known regarding specific alterations in function of the neurologic system
during pregnancy, aside from hypothalamic-pituitary neurohormonal changes.
Specific physiologic alterations resulting from pregnancy may cause the
following neurologic or neuromuscular symptoms:
•
Compression of pelvic nerves or vascular stasis caused by enlargement of the
uterus may result in sensory changes in the legs.
•
Dorsolumbar lordosis may cause pain because of traction on nerves or
compression of nerve roots.
•
Edema involving the peripheral nerves may result in carpal tunnel syndrome during
the last trimester. The syndrome is characterized by paresthesia (abnormal
sensation such as burning or tingling) and pain in the hand, radiating to the
elbow. The sensations are caused by edema that compresses the median nerve
beneath the carpal ligament of the wrist. The dominant hand is usually affected
most, although as many as 80% of women experience symptoms in both hands.
Symptoms usually regress after pregnancy. In some cases, surgical treatment may
be necessary (Cunningham et al., 2001).
•
Acroesthesia (numbness and tingling of the hands) is caused by the
stoop-shouldered stance (see Fig. 12, B) assumed by some women during
pregnancy. The condition is associated with traction on segments of the brachial
plexus.
•
Tension headache is common when anxiety or uncertainty complicates pregnancy.
However, vision problems, sinusitis, or migraine may also be responsible for headaches.
•
Light-headedness, faintness, and even syncope (fainting) are common during
early pregnancy. Vasomotor instability, postural hypotension, or hypoglycemia
may be responsible.
•
Hypocalcemia may cause neuromuscular problems such as muscle cramps or tetany.
Gastrointestinal system
Appetite. During
pregnancy, the pregnant woman's appetite and food intake fluctuate. Early in
pregnancy, some women experience "morning sickness" in response to
increasing levels of hCG and altered carbohydrate
metabolism (see Research box). Morning sickness refers to nausea with or
without vomiting. It appears at approximately 4 to 6 weeks of gestation and
usually subsides by the end of the third month (first trimester) of pregnancy.
Severity varies from mild distaste for certain foods to more severe vomiting. The
condition may be triggered by the sight or odor of various foods. Fatigue may
also be responsible for severe nausea, but further research is needed to
determine the role of this factor (O'Brien & Zhou, 1995). By the end of the
second trimester, the appetite increases in response to increasing metabolic
needs. Rarely does morning sickness have harmful effects on the embryo/fetus or
the woman. Whenever the vomiting is severe or persists beyond the first
trimester, or when it is accompanied by fever, pain, or weight loss, further
evaluation is necessary and medical intervention is likely.
Women
may also experience changes in their sense of taste, leading to cravings and
changes in dietary intake. Some women have nonfood cravings (pica) such as ice,
clay, and laundry starch (Cunningham et al., 2001).
|
RESEARCH ACUPRESSURE INTERVENTION FOR NAUSEA AND VOMITING OF PREGNANCY Up
to 70% of all pregnant women experience nausea and vomiting of pregnancy
(NVP), typically between weeks 5 through 12 of gestation.This may lead to
nutritional deficits, dehydration, and electrolyte imbalances. Employment and
family functioning may be affected. Pharmacologic treatment for NVP may cause
teratogenic effects to the fetus. Nonpharmacologic treatments, including
vitamin B6 (pyridoxine); acupressure; certain eating and drinking patterns;
and vitamin, herbal, and homeopathic remedies, are not well researched. This
clinical study investigated the use of acupressure as a treatment of NVR A total
of 110 first-trimester pregnant women with NVP were randomly assigned to
wearing Sea-Bands or placebo wrist bands. Sea-Bands are an acupressure device
consisting of an elastic band worn at the wrist that holds a button against a point 3 fingerbreadths below the wrist crease
and between the two flexor tendons on the medial forearm. The placebos had no
button. Days 1 through 4, the women wore their Sea-Band or placebo, then removed them for days 5 through 7, keeping seven
daily logs of nausea and vomiting. Results showed that the Sea-Band group had
significantly less nausea and vomiting than the placebo group while wearing
the device.The Sea-Band group also had a significant rise in nausea and
vomiting after the device was discontinued. In addition, women in the
Sea-Band group who used vitamin B6 during the treatment had significantly
more relief from nausea and vomiting than did nontakers, but this effect
disappeared when the device was removed. IMPLICATION FOR PRACTICE Alternative
and complementary treatments for women's health, including pregnancy, are
numerous. Nurses need to be informed about the most current treatments for
discomforts of pregnancy that are effective and at the same time safe,
noninvasive, and inexpensive. This study suggests that acupressure can be
recommended for relief of NVR Source: Steel,
N. et al. (2001). Effect of acupressure by Sea-Bands on nausea
and vomiting of pregnancy. J Obstet Gyncol Neonatal Nurs, 30(1), 61-70. |
Mouth. The
gums become hyperemic, spongy, and swollen during pregnancy. They tend to bleed
easily because the rising levels of estrogen cause selective increased vascularity
and connective tissue proliferation (a nonspecific gingivitis). Epulis
(discussed in the section on the integumentary system) may develop at the
gumline. Some pregnant women complain of ptyalism (excessive salivation), which
may be caused by the decrease in unconscious swallowing by the woman when
nauseated or from stimulation of salivary glands by eating starch (Cunningham et
al., 2001).
Esophagus, stomach, and intestines. Herniation
of the upper portion of the stomach (hiatal hernia) occurs after the seventh or
eighth month of pregnancy in approximately 15% to 20% of pregnant women. This
condition results from upward displacement of the stomach, which causes the
hiatus of the diaphragm to widen. It occurs more often in multiparas and older
or obese women.
Increased
estrogen production causes decreased secretion of hydrochloric acid. Therefore
peptic ulcer formation or flare-up of existing peptic ulcers is uncommon during
pregnancy.
Increased
progesterone production causes decreased tone and motility of smooth muscles,
resulting in esophageal regurgitation, slower emptying time of the stomach, and
reverse peristalsis. As a result, the woman may experience "acid
indigestion" or heartburn (pyrosis).
Iron
is absorbed more readily in the small intestine in response to increased needs
during pregnancy. Even when the woman is deficient in iron, it will continue to
be absorbed in sufficient amounts for the fetus to have a normal hemoglobin
level.
Increased
progesterone (causing loss of muscle tone and decreased peristalsis) results in
an increase in water absorption from the colon and may cause constipation.
Constipation can also result from hypoperistalsis (sluggishness of the bowel),
food choices, lack of fluids, iron supplementation, decreased activity level,
abdominal distention by the pregnant uterus, and displacement and compression of
the intestines. If the pregnant woman has hemorrhoids (see Fig. 9) and is
constipated, the hemorrhoids may become everted or may bleed during straining
at stool. A mild ileus (sluggishness and lack of movement resulting in
obstruction) that follows birth, as well as postbirth fluid loss and perineal
discomfort, contributes to continuing constipation.
Gallbladder and liver. The
gallbladder is often distended because of its decreased muscle tone during
pregnancy. Increased emptying time and thickening of bile caused by prolonged
retention are typical changes. These features, together with slight
hypercholesterolemia from increased progesterone levels, may account for the
development of gallstones during pregnancy.
Hepatic
function is difficult to appraise during pregnancy. However, only minor changes
in liver function develop. Occasionally, intrahepatic cholestasis (retention
and accumulation of bile in the liver, caused by factors within the liver)
occurs late in pregnancy in response to placental steroids and may result in
pruritus gravidarum (severe itching) with or without jaundice. These
distressing symptoms subside soon after birth.
Abdominal discomfort. Intraabdominal
alterations that can cause discomfort include pelvic heaviness or pressure, round
ligament tension, flatulence, distention and bowel cramping, and uterine
contractions. In addition to displacement of intestines, pressure from the
expanding uterus causes an increase in venous pressure in the pelvic organs.
Although most abdominal discomfort is a consequence of normal maternal
alterations, the health care provider must be constantly alert to the
possibility of disorders such as bowel obstruction or an inflammatory process.
Appendicitis
may be difficult to diagnose in pregnancy because the appendix is displaced
upward and laterally, high and to the right, away from McBurney's point (Fig.
14).
Fig. 14
Change in position of appendix in pregnancy. Note McBurney's point.
Endocrine system
Profound
endocrine changes are essential for pregnancy maintenance, normal fetal growth,
and postpartum recovery.
Pituitary and placental hormones. During
pregnancy, the elevated levels of estrogen and progesterone (produced first by
the corpus luteum in the ovary until approximately 14 weeks of gestation and
then by the placenta) suppress secretion of follicle-stimulating hormone and
luteinizing hormone by the anterior pituitary. The maturation of a follicle and
ovulation do not occur. Although the majority of women experience amenorrhea (absence
of menses), at least 20% have some slight, painless spotting during early
gestation. Implantation bleeding and bleeding following intercourse related to
cervical friability can occur. Most of the women experiencing slight gestational
bleeding continue to full term and have normal infants. However, all instances
of bleeding should be reported and evaluated.
After
implantation, the fertilized ovum and the chorionic villi produce hCG, which maintains the corpus luteum's production of
estrogen and progesterone until the placenta takes over their production
(Creasy & Resnik, 1999).
Progesterone
is essential for maintaining pregnancy by relaxing smooth muscles, resulting in
decreased uterine contractility and prevention of miscarriage. Progesterone and
estrogen cause fat to deposit in subcutaneous tissues over the maternal
abdomen, back, and upper thighs. This fat serves as an energy reserve for both
pregnancy and lactation. Estrogen also promotes the enlargement of the
genitals, uterus, and breasts and increases vascularity, causing vasodilation.
Estrogen causes relaxation of pelvic ligaments and joints. It also alters
metabolism of nutrients by interfering with folic acid metabolism, increasing
the level of total body proteins, and promoting retention of sodium and water
by kidney tubules. Estrogen may decrease secretion of hydrochloric acid and
pepsin, which may be responsible for digestive upsets such as nausea.
Serum
prolactin produced by the anterior pituitary begins to rise early in the first
trimester and increases progressively to term. It is responsible for initial
lactation; however, the high levels of estrogen and progesterone inhibit lactation
by blocking the binding of prolactin to breast tissue until after birth (Guyton
& Hall, 1997).
Oxytocin
is produced by the posterior pituitary in increasing amounts as the fetus
matures. This hormone can stimulate uterine contractions during pregnancy, but
high levels of progesterone prevent contractions until near term. Oxytocin also
stimulates the let-down or milk-ejection reflex after birth in response to the
infant sucking at the mother's breast.
Human
chorionic somatomammotropin (hCS), previously called human placental lactogen,
is produced by the placenta, acts as a growth hormone, and contributes to breast
development. It decreases the maternal metabolism of glucose and increases the
amount of fatty acids for metabolic needs (Alsat et al., 1997; Guyton &
Hall, 1997).
Thyroid gland. During
pregnancy there is an increase in gland activity and hormone production. The
increased activity is reflected in a moderate enlargement of the thyroid gland
caused by hyperplasia of the glandular tissue and increased vascularity
(Cunningham et al., 2001). Thyroxine-binding globulin increases as a result of
increased estrogen levels. This increase begins at approximately 20 weeks of
gestation. The level of total (free and bound) thyroxine (T4) increases between
6 and 9 weeks of gestation and plateaus at 18 weeks of gestation. Free T4 and free triiodothyronine (T3) return to nonpregnant levels
after the first trimester. Despite these changes in hormone production, the
pregnant woman usually does not develop hyperthyroidism (Cunningham et al.,
2001).
Parathyroid gland. Parathyroid
hormone controls calcium and magnesium metabolism. Pregnancy induces a slight
hyperparathyroidism, a reflection of increased fetal requirements for calcium
and vitamin D. The peak level of parathyroid hormone occurs between 15 and 35 weeks
of gestation when the needs for growth of the fetal skeleton are greatest.
Levels return to normal after birth.
Pancreas. The
fetus requires significant amounts of glucose for its growth and development.
To meet its need for fuel, the fetus not only depletes the store of maternal glucose
but also decreases the mother's ability to synthesize glucose by siphoning off
her amino acids. Maternal blood glucose levels fall. Maternal insulin does not
cross the placenta to the fetus. As a result, in early pregnancy, the pancreas
decreases its production of insulin.
As
pregnancy continues, the placenta grows and produces progressively larger
amounts of hormones (i.e., hCS, estrogen, and progesterone). Cortisol
production by the adrenals also increases. Estrogen, progesterone, hCS, and cortisol
collectively decrease the mother's ability to use insulin. Cortisol stimulates
increased production of insulin but also increases the mother's peripheral
resistance to insulin (i.e., the tissues cannot use the insulin). Decreasing the
mother's ability to use her own insulin is a protective mechanism that ensures
an ample supply of glucose for the needs of the fetoplacental unit. The result
is an added demand for insulin by the mother that continues to increase at a
steady rate until term. The normal beta cells of the islets of Langerhans in
the pancreas can meet this demand for insulin.
Adrenal glands. The
adrenal glands change little during pregnancy. Secretion of aldosterone is
increased, resulting in reabsorption of excess sodium from the renal tubules.
Cortisol levels are also increased (Chamberlain & Pipkin, 1998).
MATERNAL AND FETAL NUTRITION
Nutrition is one of the many factors that influence the outcome of
pregnancy (Fig. 1). However, maternal nutritional status is an especially
significant factor, both because it is potentially alterable and because good
nutrition before and during pregnancy is an important preventive measure for a
variety of problems. These problems include birth of low-birth-weight (LBW) and
preterm infants. It is essential that the importance of good nutrition be
emphasized to all women of childbearing potential. Nutrition assessment,
intervention, and evaluation must be an integral part of nursing care for all
pregnant women.
Fig,
1 Web of influences that can affect outcome of pregnancy. (From Wardlaw, G., & Insel, P. [1993]. Perspectives in nutrition.
NUTRIENT NEEDS BEFORE CONCEPTION
A
healthful diet before conception is the best way to ensure that adequate
nutrients are available for the developing fetus. Folic acid (folate) intake is
of particular concern before conception and during early gestation, because
neural tube defects (i.e., failure of the neural tube to close) are more common
in infants of women with poor folic acid intake. It is estimated that the
incidence of neural tube defects could be halved if all women had an adequate
folic acid intake during this period (Butterworth & Bendich, 1996). All
women capable of becoming pregnant are advised to consume 400 p,g of folic acid daily in fortified foods (e.g.,
ready-to-eat cereals and enriched grain products) or supplements, in addition
to a diet rich in folic acid-containing foods: green leafy vegetables, whole
grains, and meats.
Both
maternal and fetal risks in pregnancy are increased when the mother is
significantly underweight or overweight when pregnancy begins. Ideally, all
women would achieve their desirable body weights before conception.
NUTRIENT NEEDS
DURING PREGNANCY
Nutrient
needs are determined, at least in part, by the stage of gestation in that the
amount of fetal growth varies during the different stages of pregnancy. During
the first trimester the synthesis of fetal tissues places relatively few
demands on maternal nutrition. Therefore, during the first trimester, when the
embryo/fetus is very small, the needs are only slightly increased over those
before pregnancy. In contrast, the last trimester- is a period of noticeable
fetal growth when most of the deposition of fetal stores of energy sources and
minerals occurs. Basal metabolic rates, when expressed as kilocalories (kcal)
per minute, are approximately 20% higher in pregnant women than in nonpregnant women.
This increase includes the energy cost for tissue synthesis.
Dietary reference intakes (DRIs)
are a new approach that the Food and Nutrition Board of the National Academy of
Sciences has adopted to provide new nutritional recommendations for the people
of the
