• Differentiate between preterm birth and low birth weight. • Identify the major risk factors associated with spontaneous preterm birth. • Analyze current interventions to prevent spontaneous preterm birth. • Discuss the use of tocolytics and antenatal glucocorticoids in preterm labor. • Evaluate the effects of prescribed bed rest on pregnant women and their families. • Design a nursing care plan for women with preterm premature rupture of membranes (preterm PROM). • Summarize the nursing care for women having induction or augmentation of labor, forceps- and vacuum-assisted birth, cesarean birth, and vaginal birth after a cesarean birth. • Explain the care of a woman with postterm pregnancy. • Discuss obstetric emergencies and their appropriate management. preterm premature rupture of membranes (preterm PROM) Premature rupture of membranes that occurs before 37 weeks of gestation Additional related content can be found on the companion website at http://evolve.elsevier.com/Lowdermilk/Maternity/ • Animation: Breech Examination • Animation: Shoulder Dystocia • Case Study: Postdate Pregnancy • Nursing Care Plan: Dysfunctional Labor: Hypotonic Uterine Dysfunction with Protracted Active Phase • Nursing Care Plan: Preterm Labor • Spanish Guidelines: Cesarean Birth • Spanish Guidelines: Induction of Labor Preterm labor is defined as cervical changes and uterine contractions occurring between 20 and 37 weeks of pregnancy. Preterm birth is any birth that occurs before the completion of 37 weeks of gestation (Iams & Romero, 2007). It occurs in approximately 12.8% of all live births, and the rate has been increasing for the last several years. Preterm birth is the major unsolved problem in perinatal medicine today (Iams, Romero, & Creasy, 2009). Approximately 75% of all preterm births are termed late preterm births because they occur between 34 and 36 weeks of gestation. Although these babies experience significant complications, the great majority of infant deaths and the most serious morbidity occur among the 16% of all preterm infants who are born before 32 weeks of gestation (Iams et al., 2009). See Chapters 18 and 24 for more discussion of problems related to late preterm birth. Although they have distinctly different meanings, the terms preterm birth or prematurity and low birth weight were often used interchangeably in the past. Preterm birth describes the length of gestation (i.e., less than 37 weeks regardless of the weight of the infant), whereas low birth weight describes only weight at the time of birth (i.e., ≤2500 g). Because birth weight was far easier to determine than gestational age, in many settings and publications, low birth weight was used as a substitute term for preterm birth. Preterm birth, however, is a more dangerous health condition for an infant than low birth weight because a decreased length of time in the uterus correlates with immaturity of body systems. Low birth weight babies can be, but are not necessarily, preterm; low birth weight can be caused by conditions other than preterm birth, such as intrauterine growth restriction (IUGR), a condition of inadequate fetal growth not necessarily correlated with initiation of labor. On the other hand, infants born at a preterm gestation can weigh more than 2500 g at birth. Today, thanks to advances in pregnancy dating, outcomes related to gestational age can be increasingly distinguished from outcomes related to birth weight (Iams et al., 2009). The incidence of preterm birth in developed countries has increased mainly as a result of more late preterm births and multifetal gestations. An increased use of assisted reproductive technologies has led to the rise in multifetal gestations (Iams et al., 2009). An increasing willingness on the part of health care providers to end the pregnancy when maternal or obstetric conditions threaten the health of mother or fetus after 32 to 34 weeks of gestation also contributes to the rise in preterm births (Iams & Romero, 2007). Increasingly, preterm births are being divided into two categories, spontaneous and indicated. Spontaneous preterm births occur after an early initiation of the labor process. Conditions such as preterm labor with intact membranes, preterm premature rupture of membranes (preterm PROM), cervical insufficiency, or amnionitis often result in preterm birth. Approximately 75% of all preterm births in the United States are spontaneous (Iams et al., 2009). Box 22-1 lists risk factors for the development of spontaneous preterm birth. Indicated preterm births, on the other hand, occur as a means to resolve maternal or fetal risk related to continuing the pregnancy. Approximately 25% of all preterm births in the United States are indicated because of medical or obstetric conditions that affect the mother, the fetus, or both. An increase in the number of indicated preterm births accounts for much of the recent rise in late preterm births (Iams et al., 2009). Box 22-2 lists common causes of indicated preterm births. The remainder of this section deals with spontaneous preterm labor and birth. A history of previous preterm birth, multiple gestation, bleeding after the first trimester of pregnancy, and a low maternal body mass index have been shown to be major risk factors for spontaneous preterm birth (Iams & Romero, 2007). Other risk factors include non-Caucasian race (especially African-American), low socioeconomic and educational status, living with chronic stress, smoking, substance abuse, physically demanding working conditions, and periodontal disease (Iams et al., 2009). A recent study found that perceived levels of stress measured at 28 weeks of gestation in African-American women experiencing preterm labor were higher in those who gave birth prematurely than in those whose pregnancies reached term (Gennaro, Shults, & Garry, 2008). In addition, the risk for preterm birth appears to be genetically related. Relatives of women who were born prematurely or gave birth prematurely also have an increased risk for spontaneous preterm birth (Iams et al., 2009). Many risk scoring systems have been developed in an attempt to determine which women might go into labor prematurely. None of these systems has been very successful, however, because at least 50% of all women who ultimately give birth prematurely have no identifiable risk factors (Iams & Romero, 2007; Iams et al., 2009). Therefore all women should be educated about prematurity not only in early pregnancy, but also in the preconceptional period. The presence of fetal fibronectin during the late second and early third trimesters of pregnancy may be related to placental inflammation, which is thought to be one cause of spontaneous preterm labor. The presence of fetal fibronectin is not very sensitive as a predictor of preterm birth, however. Before 35 weeks of gestation a positive fetal fibronectin test predicts preterm birth only approximately 25% of the time. The test’s sensitivity may be better earlier in pregnancy. In one study the fetal fibronectin test predicted 65% of preterm births occurring before 28 weeks of gestation when it was performed between 22 and 24 weeks. The test is often used to predict who will not go into preterm labor because preterm birth is very unlikely to occur in women with a negative result. Use of the fetal fibronectin test in women who are at low risk for preterm birth as a screening tool is not recommended (Iams et al., 2009). Another possible predictor of preterm birth is endocervical length. Changes in cervical length occur before uterine activity; therefore cervical measurement can identify women in whom the labor process has begun. However, because preterm cervical shortening occurs over a period of weeks, neither digital nor ultrasound cervical examination is very sensitive at predicting imminent preterm birth (Iams et al., 2009). Women whose cervical length is more that 30 mm are unlikely to give birth prematurely even if they have symptoms of preterm labor (Iams & Romero, 2007; Iams et al., 2009). Infection is currently the only factor that has been definitely shown to cause preterm labor. Another proposed cause of preterm labor and birth is bleeding at the site of placental implantation in the uterus in the first or second trimester of pregnancy. The resulting uteroplacental ischemia or hemorrhage at the decidual layer of the placenta may somehow activate the preterm labor process. Intrauterine inflammation is associated with infection, uterine vascular compromise, and decidual hemorrhage, and may contribute to preterm labor. Maternal and fetal stress, uterine overdistention, allergic reaction, and a decrease in progesterone are other factors that may play a part in initiating preterm labor. That preterm labor is caused by multiple pathologic processes that eventually result in uterine contractions, cervical changes, or membrane rupture is becoming increasingly clear (Iams et al., 2009; Romero & Lockwood, 2009). Two recent research studies suggest that recurrent preterm birth can be prevented in some women by administering prophylactic progesterone supplementation. In one study, women were given vaginal suppositories daily. In the other, women received weekly intramuscular injections of 17-alpha hydroxyprogesterone caproate. In both studies the risk of recurrent preterm birth was reduced by approximately one third. Exactly how progesterone works to prevent recurrent preterm birth is unclear; thus more study is necessary. Another important point to note is that prophylactic supplemental progesterone administration is recommended only for women who have previously given birth prematurely (Meis & Society for Maternal-Fetal Medicine, 2005; Romero & Lockwood, 2009). Because all pregnant women must be considered at risk for preterm labor, assessment regarding knowledge of this condition begins early in pregnancy and continues throughout the prenatal period. Nursing diagnoses, interventions, and expected outcomes of care will be established for each woman based on her assessment findings (see the Nursing Process box: Preterm Labor and the Nursing Care Plan box: Preterm Labor). Nursing Care Plan Preterm Labor Nursing Diagnosis Deficient knowledge related to the recognition of preterm labor Expected Outcome Woman and significant other will verbalize the signs and symptoms of preterm labor. Nursing Interventions/Rationales • Assess what the partners know about abnormal signs and symptoms during pregnancy to identify areas of deficit. • Discuss signs and symptoms that serve as warning signs of preterm labor so that the woman or her partner has adequate information to identify problems early. • Provide written supplemental materials that include a list of warning signs and instructions regarding what to do if any of the listed signs occur so that the couple can reinforce and review learning and act swiftly and appropriately should a sign occur. • Discuss and demonstrate how to assess and time the contractions to provide needed skills to assess the signs of labor.
Labor and Birth at Risk
Web Resources
Preterm Labor and Birth
Preterm Birth versus Low Birth Weight
Predicting Spontaneous Preterm Labor and Birth
Biochemical markers
Cervical length
Causes of spontaneous preterm labor and birth
Care Management
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Case Study: Preterm Labor