Postpartum physiology. Nursing care of the Postpartum Woman. REPRODUCTIVE SYSTEM AND ASSOCIATED STRUCTURES
UTERUS
Involution process
The return of the uterus to a nonpregnant state following birth is known as involution. This process begins immediately after expulsion of the placenta with contraction of the uterine smooth muscle.
At the end of the third stage of labor the uterus is in the midline, approximately 2 cm below the level of the umbilicus, with the fundus resting on the sacral promontory. At this time, the uterus is approximately the size it was at 16 weeks of gestation (about the size of a grapefruit) and weighs approximately 1000 g.
Within 12 hours the fundus may be approximately 1 cm above the umbilicus (Fig. 1). Involution progresses rapidly during the next few days. The fundus descends 1 to 2 cm every 24 hours. By the sixth postpartum day the fundus is normally located halfway between the umbilicus and the symphysis pubis. A week after birth the uterus once again lies in the true pelvis. The uterus should not be palpable abdominally after the ninth postpartum day.
The uterus, which at full term weighs approximately 11 times its prepregnancy weight, involutes to approximately 500 g by 1 week after birth and to 350 g by 2 weeks after birth. At 6 weeks it weighs 50 to 60 g (see Fig. 1).
Increased estrogen and progesterone levels are responsible for stimulating the massive growth of the uterus during pregnancy. Prenatal uterine growth results from both hyperplasia, an increase in the number of muscle cells, and from hypertrophy, an enlargement of the existing cells. Postpartally, the decrease in these hormones causes autolysis, the self-destruction of excess hypertrophied tissue. The additional cells laid down during pregnancy remain and account for the slight increase in uterine size after each pregnancy.
Subinvolution is the failure of the uterus to return to a nonpregnant state. The most common causes of subinvolution are retained placental fragments and infection.
Contractions
Postpartum hemostasis is achieved primarily by compression of intramyometrial blood vessels as the uterine muscle contracts rather than by platelet aggregation and clot formation. The hormone oxytocin, released from the pituitary gland, strengthens and coordinates these uterine contractions, which compress blood vessels and promote hemostasis. During the first 1 to 2 postpartum hours, uterine contractions may decrease in intensity and become uncoordinated. Because it is vital that the uterus remain firm and well contracted, exogenous oxytocin (Pitocin) is usually administered intravenously or intramuscularly immediately after expulsion of the placenta. Mothers who plan to breastfeed may also be encouraged to put the baby to breast immediately after birth because suckling stimulates oxytocin release from the posterior pituitary gland.
Afterains
In first-time mothers, uterine tone is good, the fundus generally remains firm, and the mother does not perceive uterine cramping. Periodic relaxation and vigorous contraction are more common in subsequent pregnancies and may cause uncomfortable cramping called afterbirth pains (afterpains), which persist throughout the early puerperium. Afterpains are more noticeable after births in which the uterus was overdistended (e.g., large baby, multifetal gestation, polyhydramnios). Breastfeeding and exogenous oxytocic medication usually intensify these afterpains because both stimulate uterine contractions.
Placental site
Immediately after the placenta and membranes are expelled, vascular constriction and thromboses reduce the placental site to an irregular nodular and elevated area. Upward growth of the endometrium causes sloughing of necrotic tissue and prevents the scar formation that is characteristic of normal wound healing. This unique healing process enables the endometrium to resume its usual cycle of changes and to permit implantation and placentation in future pregnancies. Endometrial regeneration is completed by the end of the third postpartum week, except at the placental site. Regeneration at the placental site usually is not complete until 6 weeks after birth.
Lochia
Postchildbirth uterine discharge, commonly called lochia, initially is bright red and changes later to a pinkish red or reddish brown. It may contain small clots. For the first 2 hours after birth the amount of uterine discharge should be approximately that of a heavy menstrual period. After that time, the lochia flow should steadily decrease.
Lochia rubra consists mainly of blood and decidual and trophoblastic debris. The flow pales, becoming pink or brown (lochia serosa) after 3 to 4 days. Lochia serosa consists of old blood, serum, leukocytes, and tissue debris. Approximately 10 days after childbirth the drainage becomes yellow to white (lochia alba). Lochia alba consists of leukocytes, decidua, epithelial cells, mucus, serum, and bacteria. Lochia alba may continue for 2 to 6 weeks after the birth.
If the woman receives an oxytocic medication, the flow of lochia is usually scant until the effects of the medication wear off. The amount of lochia is usually less after cesarean births. Flow of lochia usually increases with ambulation and breastfeeding. Lochia tends to pool in the vagina when the woman is lying in bed; the woman then may experience a gush of blood when she stands. This gush should not be confused with hemorrhage.
Persistence of lochia rubra early in the postpartum period suggests continued bleeding as a result of retained fragments of the placenta or membranes. Recurrence of bleeding approximately 10 days after birth is from the healing placental site. However, any bleeding occurring 3 to 4 weeks after birth may be caused by infection or subinvolution. Continued flow of lochia serosa or lochia alba may indicate endometritis, particularly if fever, pain, or abdominal tenderness is associated with the discharge. Lochia should smell like normal menstrual flow; an offensive odor usually indicates infection.
Not all postpartal vaginal bleeding is lochia; vaginal bleeding after birth may be due to unrepaired vaginal or cervical lacerations. Table 1 distinguishes between lochial and nonlochial bleeding.
CERVIX
The cervix is soft immediately after birth. By 18 hours postpartum it has shortened, become firm, and regained its form. The cervix up to the lower uterine segment remains edematous, thin, and fragile for several days after birth. The ectocervix (portion of the cervix that protrudes into the vagina) appears bruised and has some small lacerations—optimal conditions for the development of infection. The cervical os, which dilated to 10 cm during labor, closes gradually. Two fingers may still be introduced into the cervical os for the first 4 to 6 days postpartum; however, only the smallest curette can be introduced by the end of 2 weeks. The external cervical os never regains its prepregnant appearance; it is no longer shaped like a circle but appears as a jagged slit that is often described as a “fishmouth.” Lactation delays the production of cervical and other estrogen-influenced mucus and mucosal characteristics.
VAGINA AND PERINEUM
Postpartum estrogen deprivation is responsible for the thinness of the vaginal mucosa and the absence of rugae. The greatly distended, smooth-walled vagina gradually returns to its prepregnancy size by 6 to 8 weeks after childbirth. Rugae reappear by approximately the fourth week, but they are never as prominent as they are in the nulliparous woman. Most rugae are permanently flattened. The mucosa remains atrophic in the lactating woman, at least until menstruation resumes. Thickening of the vaginal mucosa occurs with the return of ovarian function. Estrogen deficiency is also responsible for a decreased amount of vaginal lubrication. Localized dryness and coital discomfort (dyspareunia) may persist until ovarian function returns and menstruation resumes. The use of a water-soluble lubricant during sexual intercourse is usually recommended.
Initially, the introitus is erythematous and edematous, especially in the area of the episiotomy or laceration repair. It is barely distinguishable from that of a nulliparous woman if lacerations and an episiotomy have been carefully repaired, hematomas are prevented or treated early, and the woman observes good hygiene during the first 2 weeks after birth.
Most episiotomies are visible only if the woman is lying on her side with her upper buttock raised or if she is placed in the lithotomy position. A good light source is essential for visualization of some episiotomies. Healing of an episiotomy is the same as any surgical incision. Signs of infection (pain, redness, warmth, swelling, or discharge) or loss of approximation (separation of the edges of the incision) may occur. Healing should occur within 2 to 3 weeks.
Hemorrhoids (anal varicosities) are commonly seen. Internal hemorrhoids may evert while the woman is pushing during birth. Women often experience associated symptoms such as itching, discomfort, and bright red bleeding with defecation. Hemorrhoids usually decrease in size within 6 weeks of childbirth.
Pelvic muscular support
The supporting structure of the uterus and vagina may be injured during childbirth and may contribute to later gynecologic problems. Supportive tissues of the pelvic floor that are torn or stretched during childbirth may require up to 6 months to regain tone. Kegel exercises, which help to strengthen perineal muscles and encourage healing, are recommended after childbirth. Later in life, women can experience pelvic relaxation, the lengthening and weakening of the fascial supports of pelvic structures. These structures include the uterus, upper posterior vaginal wall, urethra, bladder, and rectum.
ENDOCRINE SYSTEM
PLACENTAL HORMONES
Significant hormonal changes occur during the postpartal period. Expulsion of the placenta results in dramatic decreases of the hormones produced by that organ. Decreases in human chorionic somatomammotropin, estrogens, cortisol, and the placental enzyme insulinase reverse the diabetogenic effects of pregnancy, resulting in significantly lower blood sugar levels in the immediate puerperium. Mothers with type 1 diabetes will be likely to require much less insulin for several days after birth. Because these normal hormonal changes make the puerperium a transitional period for carbohydrate metabolism, it is more difficult to interpret glucose tolerance tests.
Estrogen and progesterone levels drop markedly after expulsion of the placenta and reach their lowest levels 1 week postpartum. Decreased estrogen levels are associated with breast engorgement and with the diuresis of excess extracellular fluid accumulated during pregnancy. Ionlactating women, estrogen levels begin to rise by 2 weeks after birth and by postpartum day 17 are higher than in women who breastfeed (Bowes & Katz, 2002).
β-Human chorionic gonadotropin (/3-hCG) disappears from maternal circulation in 14 days (Resnik, 1999).
PITUITARY HORMONES AND OVARIAN FUNCTION
Lactating and nonlactating women differ considerably in the time when the first ovulation occurs and when menstruation resumes. The persistence of elevated serum prolactin levels in breastfeeding women appears to be responsible for suppressing ovulation. Because levels of follicle-stimulating hormone (FSH) have been shown to be identical in lactating and nonlactating women, it is thought that the ovulation is suppressed in lactating women because the ovary does not respond to FSH stimulation when increased prolactin levels are present (Resnik, 1999).
Prolactin levels in blood rise progressively throughout pregnancy. In women who breastfeed, prolactin levels remain elevated into the sixth week after birth (Rebar, 1999). Serum prolactin levels are influenced by the frequency of breastfeeding, the duration of each feeding, and the degree to which supplementary feedings are used. Individual differences in the strength of an infant’s sucking stimulus probably also affect prolactin levels. Ionlactating women, prolactin levels decline after birth and reach the prepregnant range in 4 to 6 weeks (Rebar, 1999).
Ovulation occurs as early as 27 days after birth in nonlactating women, with a mean time of 70 to 75 days. Approximately 70% of nonbreastfeeding women resume menstruating by 3 months after birth. In women who breastfeed, the mean length of time to initial ovulation is 17 weeks. In lactating women, both resumption of ovulation and return of menses are determined in large part by breastfeeding patterns (Resnik, 1999). Many women ovulate before their first postpartum menstrual period occurs; thus there is need to discuss contraceptive options early in the puerperium (Rebar, 1999).
The first menstrual flow after childbirth is usually heavier thaormal. Within three to four cycles the amount of menstrual flow returns to the woman’s prepregnancy volume.
ABDOMEN
When the woman stands up during the first days after birth, her abdomen protrudes and gives her a still-pregnant appearance. During the first 2 weeks after birth the abdominal wall is relaxed. It takes approximately 6 weeks for the abdominal wall to return almost to its nonpregnancy state. The skin regains most of its previous elasticity, but some striae may persist. The return of muscle tone depends on previous tone, proper exercise, and the amount of adipose tissue. Occasionally, with or without overdistention because of a large fetus or multiple fetuses, the abdominal wall muscles separate, a condition termed diastasis recti abdominis (see Fig. 8-13). Persistence of this defect may be disturbing to the woman, but surgical correction rarely is necessary. With time, the defect becomes less apparent.
URINARY SYSTEM
The hormonal changes of pregnancy (i.e., high steroid levels) contribute to an increase in renal function; diminishing steroid levels after childbirth may partly explain the reduced renal function that occurs during the puerperium. Kidney function returns to normal within 1 month after birth. From 2 to 8 weeks are required for the pregnancy-induced hypotonia and dilation of the ureters and renal pelves to return to the nonpregnant state (Resnik, 1999). In a small percentage of women, dilation of the urinary tract may persist for 3 months, which increases the chance of developing a urinary tract infection.
URINE COMPONENTS
The renal glycosuria induced by pregnancy disappears, but lactosuria may occur in lactating women. The blood urea nitrogen increases during the puerperium as autolysis of the involuting uterus occurs. This breakdown of excess protein in the uterine muscle cells also results in a mild (+1) proteinuria for 1 to 2 days after childbirth in approximately 50% of women (Simpson & Creehan, 2001). Ketonuria may occur in women with an uncomplicated birth or after a prolonged labor with dehydration.
POSTPARTAL DIURESIS
Within 12 hours of birth, women begin to lose excess tissue fluid accumulated during pregnancy. Profuse diaphoresis often occurs, especially at night, for the first 2 or 3 days after childbirth. Postpartal diuresis, caused by decreased estrogen levels, removal of increased venous pressure in the lower extremities, and loss of the remaining pregnancy-induced increase in blood volume, also aids the body to rid itself of excess fluid. Fluid loss through perspiration and increased urinary output accounts for a weight loss of approximately 2.25 kg during the puerperium.
URETHRA AND BLADDER
Birth-induced trauma, increased bladder capacity following childbirth, and the effects of conduction anesthesia combine to cause a decreased urge to void. In addition, pelvic soreness caused by the forces of labor, vaginal lacerations, or the episiotomy reduces or alters the voiding reflex. Decreased voiding combined with postpartal diuresis may result in bladder distention. Immediately after birth, excessive bleeding can occur if the bladder becomes distended because it pushes the uterus up and to the side and prevents the uterus from contracting firmly. Later in the puerperium overdistention can make the bladder more susceptible to infection and impede the resumption of normal voiding (Resnik, 1999). With adequate emptying of the bladder, bladder tone is usually restored 5 to 7 days after childbirth.
GASTROINTESTINAL SYSTEM
APPETITE
The mother usually is hungry shortly after the birth and can tolerate a light diet. Most new mothers are very hungry after full recovery from analgesia, anesthesia, and fatigue. Requests for double portions of food and frequent snacks are not uncommon (see Research box).
BOWEL EVACUATION
A spontaneous bowel evacuation may not occur for 2 to 3 days after childbirth. This delay can be explained by decreased muscle tone in the intestines during labor and the immediate puerperium, prelabor diarrhea, lack of food, or dehydration. The mother often anticipates discomfort during the bowel movement because of perineal tenderness as a result of episiotomy, lacerations, or hemorrhoids and resists the urge to defecate. Regular bowel habits should be reestablished when bowel tone returns.
Obstetric trauma (e.g., direct injury to the sphincter muscle, damage to the innervation of the pelvic floor) is perhaps the leading cause of anal incontinence in otherwise healthy women (Toglia, 1996). Women should be taught during pregnancy about episiotomy and its possible sequelae. Pelvic floor (Kegel) exercises should be encouraged.
BREASTS
Promptly after birth, there is a decrease in the concentrations of hormones (i.e., estrogen, progesterone, hCG, prolactin, cortisol, and insulin) that stimulated breast development during pregnancy. The time it takes for these hormones to return to prepregnancy levels is determined in part by whether the mother breastfeeds her infant.
BREASTFEEDING MOTHERS
As lactation is established, a mass (lump) may be felt in the breast. Unlike the lumps associated with fibrocystic breast disease or cancer (which may be consistently palpated in the same location), a filled milk sac shifts position from day to day. Before lactation begins, the breasts feel soft and a yellowish fluid, colostrum, can be expressed from the nipples. After lactation begins, the breasts feel warm and firm. Tenderness may persist for approximately 48 hours after the start of lactation. Bluish-white milk with a skim-milk appearance (true milk) can be expressed from the nipples. The nipples are examined for erectility and signs of irritation such as cracks, blisters, or reddening.
NONBREASTFEEDING MOTHERS
The breasts generally feel nodular in contrast to the granular feel of breasts ionpregnant women. The nodularity is bilateral and diffuse. Prolactin levels drop rapidly. Colostrum is present for the first few days after childbirth. Palpation of the breast on the second or third day, as milk production begins, may reveal tissue tenderness in some women. On the third or fourth postpartum day, engorgement may occur. The breasts are distended (swollen), firm, tender, and warm to the touch (because of vasocongestion). Breast distention is caused primarily by the temporary congestion of veins and lymphatics rather than by an accumulation of milk. Milk is present but should not be expressed. Axillary breast tissue (the tail of Spence) and any accessory breast or nipple tissue along the milk line may be involved. Engorgement resolves spontaneously, and discomfort decreases usually within 24 to 36 hours. A breast binder or tight bra, ice packs, or mild analgesics may be used to relieve discomfort. Nipple stimulation is avoided. If suckling is never begun (or is discontinued), lactation ceases within a few days to a week.
CARDIOVASCULAR SYSTEM
BLOOD VOLUME
Changes in blood volume after birth depend on several factors, such as blood loss during childbirth and the amount of extravascular water (physiologic edema) mobilized and excreted. Blood loss results in an immediate but limited decrease in total blood volume. Thereafter, most of the blood volume increase during pregnancy (1000 to 1500 ml) is eliminated within the first 2 weeks after birth, with return to nonpregnancy values by 6 weeks postpartum (Simpson & Creehan, 2001).
Pregnancy-induced hypervolemia (an increase in blood volume of at least 40% more than prepregnancy values near term) allows most women to tolerate considerable blood loss during childbirth. Many women lose approximately 300 to 400 ml of blood during vaginal birth of a single fetus and approximately twice this much during cesarean birth.
Readjustments in the maternal vasculature after childbirth are dramatic and rapid. The woman’s response to blood loss during the early puerperium differs from that in a nonpregnant woman. Three postpartal physiologic changes protect the woman by increasing the blood volume: (1) elimination of uteroplacental circulation reduces the size of the maternal vascular bed by 10% to 15%, (2) loss of placental endocrine function removes the stimulus for vasodilation, and (3) mobilization of extravascular water stored during pregnancy occurs. Thus hypovolemic shock usually does not occur in women who experience a normal blood loss.
CARDIAC OUTPUT
Pulse rate, stroke volume, and cardiac output increase throughout pregnancy. Immediately after the birth they remain elevated or rise even higher for 30 to 60 minutes as the blood that was shunted through the uteroplacental circuit suddenly returns to the maternal systemic venous circulation. Data regarding the exact time of return of cardiac hemodynamic levels to normal are not available, but cardiac output values remain elevated for at least 48 hours after birth, decrease rapidly in the first 2 weeks postpartum, and return to prepregnancy level by 24 weeks postpartum. Stroke volume, cardiac output, end-diastolic volume, and systemic vascular resistance values have been shown to remain greatly elevated for as long as 12 weeks postpartum (Resnik, 1999).
VITAL SIGNS
Few alterations in vital signs are seen under normal circumstances. There may be a small, transient rise in both systolic and diastolic blood pressure that lasts approximately 4 days after the birth (Table 2). Respiratory function returns to nonpregnant levels by 6 to 8 weeks after birth. After the uterus is emptied, the diaphragm descends, the normal cardiac axis is restored, and the point of maximal impulse and the electrocardiogram are normalized.
BLOOD COMPONENTS
Hematocrit and hemoglobin
During the first 72 hours after childbirth, there is a greater loss of plasma volume than in the number of blood cells. This results in a rise in hematocrit and hemoglobin levels by the seventh day after the birth. There is no increased red blood cell (RBC) destruction during the puerperium, but any excess will disappear gradually in accordance with the life span of the RBC. The exact time at which RBC volume returns to prepregnancy values is not known, but it is withiormal limits when measured 8 weeks after childbirth (Bowes & Katz, 2002).
White blood cell count
Normal leukocytosis of pregnancy averages approximately 12,000/mm3. During the first 10 to 12 days after childbirth, values between 20,000 and 25,000/mm3 are common. Neutrophils are the most numerous white blood cells. Leukocytosis coupled with the normal increase in erythrocyte sedimentation rate that occurs may obscure the diagnosis of acute infections at this time.
Coagulation factors
Clotting factors and fibrinogen are normally increased during pregnancy and remain elevated in the immediate puerperium. When combined with vessel damage and immobility, this hypercoagulable state causes an increased risk of thromboembolism, especially after a cesarean birth. Fibrinolytic activity also increases during the first few days after childbirth (Bowes & Katz, 2002). Factors I, II, VIII, IX, and X decrease within a few days to nonpregnant levels. Fibrin split products, probably released from the placental site, can also be found in maternal blood.
VARICOSITIES
Varicosities (varices) of the legs and around the anus (hemorrhoids) are common during pregnancy. Varices, even the less common vulvar varices, regress (empty) rapidly immediately after childbirth. Surgical repair of varicosities is not considered during pregnancy. Total or nearly total regression of varicosities is expected after childbirth.
