LABOR AND BIRTH AT RISK
Prepared by assistant professor N.Petrenko, MD, PhD
DYSTOCIA
Dystocia is long, difficult, or abnormal labor; it is caused by various conditions associated with the five factors affecting labor. It is estimated that dystocia occurs in approximately 8% to 11% of women during the first stage of labor when the fetus is in a vertex presentation. Secondstage dystocia is equally as common (Wiznitzer, 1995).
Dystocia can be caused by any of the following:
• Dysfunctional labor, resulting in ineffective uterine contractions or maternal bearing-down efforts (the powers); the most common cause of dystocia (Cunningham et al., 2001)
• Alterations in the pelvic structure (the passage)
• Fetal causes, including abnormal presentation or position, anomalies, excessive size, and number of fetuses (the passenger)
• Maternal position during labor and birth
• Psychologic responses of the mother to labor related to past experiences, preparation, culture and heritage, and support system
These factors are interdependent. In assessing the woman for an abnormal labor pattern, the nurse must consider the way in which these factors interact and influence labor progress. Dystocia is suspected when there is an alteration in the characteristics of uterine contractions, a lack of progress in the rate of cervical dilation, or a lack of progress in fetal descent and expulsion.
DYSFUNCTIONAL LABOR
Dysfunctional labor is described as abnormal uterine contractions that prevent the normal progress of cervical dilation, effacement (primary powers), or descent (secondary powers). Dysfunction of uterine contractions can be further described as being hypertonic or hypotonic.
Several factors seem to increase a woman’s risk for uterine dystocia, including the following:
• Body build (e.g., 30 pounds or more overweight, short stature)
• Uterine abnormalities (e.g., congenital malformations, overdistention as with multiple gestation or hydramnios)
• Malpresentations and positions of the fetus
• Cephalopelvic disproportion
• Overstimulation with oxytocin
• Maternal fatigue, dehydration and electrolyte imbalance, and fear
• Inappropriate timing of analgesic or anesthetic administration
Research has also documented a familial occurrence of dystocia. Laboring women whose mothers or sisters experienced dystocia during their labors had an increased risk for experiencing dystocia themselves, possibly related to a genetic factor affecting uterine activity (Berg-Lekas, Hogberg, & Winkvist, 1998).
Hypertonic uterine dysfunction
The woman experiencing hypertonic uterine dysfunction, or primary dysfunctional labor, often is an anxious first-time mother who is having painful and frequent contractions that are ineffective in causing cervical dilation or effacement to progress. These contractions usually occur in the latent stage (cervical dilation of less than 4 cm) and are usually uncoordinated (Fig. 4). The force of the contractions may be in the midsection of the uterus rather than in the fundus, and the uterus is therefore unable to apply downward pressure to push the presenting part against the cervix. The uterus may not relax completely between contractions (Gilbert & Harmon, 1998; Varney, 1997).
Women experiencing hypertonic uterine dysfunction may be exhausted and express concern about loss of control because of the intense pain they are experiencing and the lack of progress. Therapeutic rest, which is achieved with a warm bath or shower and the administration of analgesics such as morphine, meperidine (Demerol), or nalbuphine (Nubain) to inhibit uterine contractions, reduce pain, and encourage sleep, is usually prescribed for the management of hypertonic uterine dysfunction. After a 4- to 6-hour rest these women are likely to awaken in active labor with a normal uterine contraction pattern (Gilbert & Harmon, 1998).
Hypotonic uterine dysfunction
The second and more common type of uterine dysfunction is hypotonic uterine dysfunction, or secondary uterine inertia. The woman, who may be in her first or a subsequent pregnancy, initially makes normal progress into the active stage of labor; then the contractions become weak and inefficient or stop altogether (see Fig. 4). The uterus is easily indented, even at the peak of contractions. Intrauterine pressure during the contraction (usually less than 25 mm Hg) is insufficient for progress of cervical effacement and dilation (Gilbert & Harmon, 1998). Cephalopelvic disproportion and malpositions are common causes of this type of uterine dysfunction.
A woman experiencing hypotonic uterine dysfunction may become exhausted and be at increased risk for infection. Management usually consists of performing an ultrasound examination to rule out cephalopelvic disproportion and assessing the fetal heart rate and pattern, characteristics of amniotic fluid if membranes are ruptured, and maternal well-being. If findings are normal, measures such as ambulation, hydrotherapy, an enema, stripping or rupture of membranes, nipple stimulation, and oxytocin infusion can be used to augment the progress of labor (Varney, 1997).
Secondary powers
Secondary powers, or bearing-down efforts, are compromised when large amounts of analgesic are given. Anesthesia may also block the bearing-down reflex and, as a result, alter the effectiveness of voluntary efforts (Mayberry et al., 1999). Exhaustion resulting from lack of sleep or long labor and fatigue resulting from inadequate hydration and food intake affect the woman’s voluntary efforts. Maternal position can work against the forces of gravity and decrease the strength and efficiency of the contractions. Table 2 summarizes the characteristics of dysfunctional labor.
Alterations in pelvic structure
Pelvic dystocia. Pelvic dystocia can occur whenever there are contractures of the pelvic diameters that reduce the capacity of the bony pelvis, including the inlet, midpelvis, outlet, or any combination of these planes.
Disproportion of the pelvis is the least common cause of dystocia (Cunningham et al., 2001). Pelvic contractures may be caused by congenital abnormalities, maternal malnutrition, neoplasms, or lower spinal disorders. An immature pelvic size predisposes some adolescent mothers to pelvic dystocia. Pelvic deformities may also be the result of automobile or other accidents.
An inlet contracture is diagnosed whenever the diagonal conjugate is less than 11.5 cm. The incidence of face and shoulder presentation is increased. Because these presentations interfere with engagement and fetal descent, the risk of prolapse of the umbilical cord is increased. Inlet contracture is associated with maternal rickets and a flat pelvis. Weak uterine contractions may be noted during the first stage of labor in affected women.
Midplane contracture, the most common cause of pelvic dystocia, is diagnosed whenever the sum of the interischial spinous and posterior sagittal diameters of the midpelvis is 13.5 cm or less. Fetal descent is arrested (transverse arrest of the fetal head) in such births because the head cannot rotate internally. These infants are usually born by cesarean, but vacuum-assisted birth has been used safely when the cervix is fully dilated. Midforceps-assisted birth usually is not done because of the increased perinatal morbidity associated with this intervention.
Outlet contracture exists when the interischial diameter is 8 cm or less. It rarely occurs in the absence of midplane contracture. Women with outlet contracture have a long, narrow pubic arch and an android pelvis, and this causes fetal descent to be arrested. Maternal complications include extensive perineal lacerations during vaginal birth because the fetal head is pushed posteriorly.
Soft tissue dystocia. Soft tissue dystocia results from obstruction of the birth passage by an anatomic abnormality other than that involving the bony pelvis. The obstruction may result from placenta previa (low-lying placenta) that partially or completely obstructs the internal os of the cervix. Other causes, such as leiomyomas (uterine fibroids) in the lower uterine segment, ovarian tumors, and a full bladder or rectum, may prevent the fetus from entering the pelvis. Occasionally, cervical edema occurs during labor when the cervix is caught between the presenting part and the symphysis pubis or when the woman begins bearing-down efforts prematurely, thereby inhibiting complete dilation. Sexually transmitted infections (e.g., human papillomavirus) can alter cervical tissue integrity and thus interfere with adequate effacement and dilation. Bandl’s ring, a pathologic retraction ring, is associated with prolonged rupture of membranes and protracted labor (Cunningham et al., 2001).
Fetal causes
Dystocia of fetal origin may be caused by anomalies, excessive fetal size and malpresentation, malposition, or multifetal pregnancy. Complications associated with dystocia of fetal origin include neonatal asphyxia, fetal injuries or fractures, and maternal vaginal lacerations. Although spontaneous vaginal birth is possible in these instances, a low-forceps-assisted, vacuum-assisted, or cesarean birth often is necessary.
Anomalies. Gross ascites, large tumors, and opeeural tube defects (e.g., myelomeningocele, hydrocephalus) are fetal anomalies that can cause dystocia. The anomalies affect the relationship of the fetal anatomy to the maternal pelvic capacity, with the result that the fetus is unable to descend through the birth canal.
Cephalopelvic disproportion. Cephalopelvic disproportion (CPD), also called fetopelvic disproportion, is related to excessive fetal size (i.e., 4000 g or more). It occurred at a rate of 18.3 per 1000 live births in 1999 (Ventura et al., 2001).
When CPD is present, the fetus cannot fit through the maternal pelvis to be born vaginally. Excessive fetal size, or macrosomia, is associated with maternal diabetes mellitus, obesity, multiparity, or the large size of one or both parents. If the maternal pelvis is too small, abnormally shaped, or deformed, CPD may be of maternal origin. In this case the fetus may be of average size or even smaller.
Malposition. The most common fetal malposition is persistent occipitoposterior position (i.e., right occipitoposterior or left occipitoposterior), occurring in approximately 25% of all labors. Labor, especially the second stage, is prolonged; the woman typically complains of severe back pain from the pressure of the fetal head (occiput) pressing against her sacrum. Box 24-9 identifles suggested measures to relieve back pain and facilitate rotation of the fetal occiput to an anterior position, which will facilitate birth (Gilbert & Harmon, 1998; Simkin, 1995).
Malpresentation. Breech presentation is the most common form of malpresentation, occurring in 3% to 4% of all births and as many as 25°/o of preterm births. There are four main types of breech presentation: frank breech (thighs flexed, knees extended); complete breech (thighs and knees flexed); and two types of incomplete breech, one in which the knee extends below the buttocks and the other in which the foot extends below the buttocks (Fig. 5). Breech presentations are associated with multifetal gestation, preterm birth, fetal and maternal anomalies, hydramnios, and oligohydramnios. Diagnosis is made by abdominal palpation and vaginal examination and usually is confirmed by ultrasound scan (Laros, Flanagan, & Kilpatrick, 1995; Ventura et al, 2001).
During labor, the descent of the fetus in a breech presentation may be slow because the breech is not as good a dilating wedge as the fetal head; the labor itself usually is not prolonged. There is risk of prolapse of the cord if the membranes rupture in early labor. The presence of meconium in amniotic fluid is not necessarily a sign of fetal distress because it results from pressure on the fetal abdominal wall as it traverses the birth canal. Assessment of fetal heart rate (FHR) and pattern should be used to determine whether the passage of meconium is an expected finding associated with breech presentation or is a nonreassuring sign associated with fetal hypoxia. The fetal heart tones of infants in a breech position are best heard at or above the umbilicus.
Vaginal birth is accomplished by mechanisms of labor that manipulate the buttocks and lower extremities as they emerge from the birth canal (Varney, 1997) (Fig. 6). Piper forceps sometimes are used to deliver the head. External cephalic version (ECV) may be tried to turn the fetus to a vertex presentation.
Although opinions vary, a cesarean birth is commonly performed when the fetus is estimated to be larger than 3800 g or smaller than 1500 g, if this is a first pregnancy, if labor is ineffective, or if complications occur (Scott, 1999). Although cesarean birth reduces the risks to the fetus, the maternal risks are increased. ECV also poses risks and is not always successful. Women whose breech presentation occurs late in pregnancy need to be informed of the options for birth, as well as the risks associated with each option.
Face and brow presentations are uncommon and are associated with fetal anomalies, pelvic contractures, and CPD. Vaginal birth is possible if the fetus flexes to a vertex presentation, although forceps often are used. Cesarean birth is indicated if the presentation persists, if there is fetal distress, or if labor stops progressing.
Cesarean birth is usually necessary for a fetus in a shoulder presentation (i.e., the fetus is in a transverse lie), although ECV may be attempted after 38 weeks of gestation (Cunningham et al., 2001; Varney, 1997).
Multifetal pregnancy. Multifetal pregnancy is the gestation of twins, triplets, quadruplets, or more infants. Since 1980, the twin birthrate has increased by 53%. The twin birthrate was 28.9 per 1000 live births in 1999. The higher-order multiple birthrate (i.e., triplet and more) was 184.9 per 100,000 live births in 1999, representing the first decline in what had been a rapid escalation since 1980 (Ventura et al., 2001). It is likely that the rapid escalation was related to use of fertility-enhancing medications and procedures and the older age of childbearing. Refinements in the treatments used to treat infertility may be responsible for the recent decline in higher-order multiple births.
Multiple births are associated with more maternal complications (e.g., dysfunctional labor, hemorrhage) than are single births. The higher incidence of maternal complications and higher risk of perinatal mortality primarily stems from the birth of low-birth-weight infants resulting from preterm birth or IUGR in part related to placental dysfunction and twin-to-twin transfusion. Fetuses may experience distress and asphyxia during the birth process as a result of cord prolapse and the onset of placental separation with the birth of the first fetus.
In addition, fetal complications such as congenital anomalies and abnormal presentations can result in dystocia and an increased incidence of cesarean birth. For example, in only half of all twin pregnancies do both fetuses present in the vertex position, the most favorable for vaginal birth; in one third of the pregnancies, one twin may present in the vertex position and one in the breech (Cunningham et al., 2001; Ellings, Newman, & Bowers, 1998).
The health status of the mother may be compromised by an increased risk for hypertension, anemia, and hemorrhage associated with uterine atony, abruptio placentae, and multiple or adherent placentas. Duration of the phases and stages of labor may vary from the duration experienced with singleton births.
Teamwork and planning are essential components of the management of childbirth in multiple pregnancies. Early detection and care of complications associated with multiple births is essential to achieve a positive outcome for mother and babies. Maternal positioning and active support are used to enhance labor progress and placental perfusion. Emotional support that includes expression of feelings and full explanations of events as they occur and of the status of the mother and the fetuses/newborns is important to reduce the anxiety and stress the mother and her family experience (Ellings, Newman, & Bowers, 1998).
Position of the woman
The functional relationships between the uterine contractions, the fetus, and the mother’s pelvis are altered by the maternal position. In addition, the position can provide either a mechanical advantage or disadvantage to the mechanisms of labor by altering the effects of gravity and the body part relationships important to the progress of labor. For example, the hands-and-knees position facilitates rotation from a posterior occiput position more effectively than does the lateral position. Sitting and squatting facilitate fetal descent during pushing and shorten the second stage of labor (Biancuzzo, 1993). Discouraging maternal movement or restricting labor to the recumbent or lithotomy position may compromise progress. The incidence of dystocia in women confined to these positions is increased, resulting in increased need for augmentation of labor or the use of forceps-assisted, vacuum-assisted, or cesarean birth.
Psychologic responses
Hormones released in response to stress can cause dystocia. Sources of stress vary for each woman, but pain and the absence of a support person are two recognized factors. Confinement to bed and restriction of maternal movement can be a source of psychologic stress that compounds the physiologic stress caused by immobility in the nonmedicated laboring woman. When anxiety is excessive, it can inhibit cervical dilation and result in prolonged labor and increased pain perception. Anxiety also causes increased levels of stress-related hormones (e.g., betaendorphin, adrenocorticotropic hormone, cortisol, epinephrine). These hormones act on the smooth muscles of the uterus; increased levels can cause dystocia by reducing uterine contractility (Biancuzzo, 1993).
Abnormal labor patterns
In 1999 prolonged labor patterns occurred at a rate of 7.9 per 1000 live births. The incidence of prolonged labor patterns was slightly higher (i.e., 8.4) among women who were under 20 years of age (Ventura et al., 2001).
Six abnormal labor patterns have been identified and classified by Friedman (1989) according to the nature of the cervical dilation and fetal descent. The labor patterns seen iormal and abnormal labor are described in Table 3.
These patterns may result from a variety of causes, including ineffective uterine contractions, pelvic contractures, CPD, abnormal fetal presentations or position, early use of analgesics, conduction anesthesia, and anxiety and stress. Progress in either the first or second stage of labor can be protracted (prolonged) or arrested (stopped). Abnormal progress can be identified by plotting cervical dilation and fetal descent on a labor graph (partogram) at various intervals after the onset of labor and comparing the resulting curve with the expected labor curve for a nulliparous or multiparous labor.
Health care providers must be careful when diagnosing a labor pattern as prolonged and when intervening based on this diagnosis. Criteria defining the differences between false, latent, and active labor should be established. Using hospital admission areas to evaluate a woman’s labor status is helpful in preventing the premature implementation of labor interventions such as induction of epidural anesthesia. If a woman is found to be in false or latent (early) labor she can be sent home or remain in the admissions area until labor becomes active (McNiven et al., 1998).
Maternal morbidity and death may occur as a result of uterine rupture, infection, serious dehydration, and postpartum hemorrhage, all possible consequences of abnormal labor patterns. The fetus is at increased risk for hypoxia. A long and difficult labor also can have an adverse psychologic effect on the mother, father, and family.
Precipitous labor. Precipitous labor occurred at a rate of 19.9 per 1000 live births in 1999. Precipitous labor occurred at a slightly higher rate among women ages 35 to 54 and at the lowest rate (i.e., 14.3) among women younger than 20 years of age (Ventura et al., 2001).
Precipitous labor may result from hypertonic uterine contractions that are tetanic in intensity. Maternal and fetal complications can occur as a result. Maternal complications include uterine rupture, lacerations of the birth canal, amniotic fluid embolism, and postpartum hemorrhage. Fetal complications include hypoxia caused by decreased periods of uterine relaxation between contractions and intracranial hemorrhage related to rapid birth (Cunningham et al., 2001).
Women who have experienced precipitous labor often describe feelings of disbelief that their labor began so quickly, alarm that their labor progressed so rapidly, panic about the possibility they would not make it to the hospital on time to give birth, and finally relief when they arrived at the hospital. In addition, women have expressed frustration wheurses would not believe them when they reported their readiness to push. Some women have difficulty remembering the details of their labor and birth and require others, including caregivers, to help them fill in the gaps in their memory (Rippin-Sisler, 1996).
