A major goal of multi fetal prenatal care is accurate prediction of women likely to experience preterm delivery. Within the past decade, cervical length has been shown to be a potent predictor of preterm labor and delivery. To and associates (2006) so no graphically measured cervical length in 1163 twin pregnancies at 22 to 24 weeks' gestation. Rates of preterm delivery before 32 weeks were 66 percent in those with cervical lengths of 10 mm; 24 percent for lengths of 20 mm; and only 1 percent for 40 mm. In one review, Conde-Agudelo and coworkers (2010) concluded that a cervical length <20 mm was most accurate for predicting birth before 34 weeks, with a speciicity of 97 percent and positive likelihood ratio of 9.0. Kindinger and colleagues (2016) noted that prediction depended on both cervical length and gestational age at ascertainment. One study compared serial cervical length measurements with a single midgestation measurement. hese authors found that multiple assessments were more accurate to determine the risk of pre term twin birth in asymptomatic women (Melamed, 2016a). In another study, a change in cervical length :0.2 cm identified pregnancies at risk for delivery before 35 weeks (Moroz, 2017). Interestingly, a closed internal os by digital examination was found to be as predictive of postponed delivery as was the combination of a normal sonographically measured cervical length and negative fetal fibronectin test result (McMahon, 2002). Unfortunately, cervical length assessment in twin pregnancies has not been associated with improved outcomes (Gordon, 2016).
• Prevention of Preterm Birth
Several schemes have been evaluated to prevent preterm labor and delivery. In recent years, some have been shown to decrease the risk of pre term delivery, but only in subgroups of singleton pregnancies. In general, most have been disappointingly ineffective for both singleton and multifetal pregnancies (American College of Obstetricians and Gynecologists, 2016).
The bulk of evidence suggests that routine hospitalization does not prolong multifetal pregnancy. In one metaanaly sis, the practice did not reduce the risk of preterm birth or perinatal mortality (Crowther, 2010). At Parkland Hospital, elective hospitalization was compared with outpatient manage ment, and no advantages were found (Andrews, 1991). Impor tantly, however, almost half of women managed as outpatients required admission for specific indications such as hypertension or threatened preterm delivery.
Limited physical activity, early work leave, more frequent health-care visits and sonographic examinations, and structured advocated to reduce pre term birth rates in women with mul tiple fetuses. However, little evidence suggests that these mea sures substantially change outcome.
his has not been studied extensively in multifetl pregnancies. In one review of prophylactic oral beta-mimetic therapy that included 374 twin pregnancies, treatment did not reduce the rate of twins delivering before 37 or before 34 weeks' gestation (Ymasmit, 2015). In light of the Food and Drug Administration warning against the use of oral terbutaline because of maternal side efects, the prophylactic use of beta-mimetic drugs in multifetal gestations seems unwarranted.