As noted earlier (p. 882), serial sonographic examinations are usually performed throughout the third trimester to search for abnormal fetal growth and assess amnionic fluid volume. Associated oligohydramnios may indicate utero placental pathology and should prompt further evaluation of fetal well-being. That said, quantiYing amnionic luid volume in multifetal gestation is sometimes diicult. Some measure the deepest vertical pocket in each sac or assess the luid subjectively. Magann and coworkers (2000) compared subjective assessment and several objective methods of assessing amnionic fluid volume in 23 sets of twins. They found all methods to be equally poor in predicting abnormal volumes in diamnionic wins. At Parkland Hospital, the single deepest vertical pocket is measured in each sac. A measurement < 2 em is considered oligohydramnios, and a measurement > 8 cm is considered hydramnios (Duryea, 2017; Hernandez, 2012).
Of surveillance methods, the nons tress test or biophysical profile is often selected for twin or higher-order multifetal gestations. Because of the complex complications associated with these gestations and the potential technical diiculties in differentiating fetuses during antepartum testing, the usefulness of these methods appears limited. According to DeVoe (2008), the few exclusive studies of nonstress testing in twins suggest that the method performs the same as in singleton pregnancies.
Elliott and Finberg (1995) used the biophysical profile as the primary method for monitoring higher-order multifetal gestations. They reported that four of 24 monitored pregnancies had a poor outcome despite reassuring biophysical proile scores. Although biophysical testing is commonly performed in multifetal gestations, there are insuicient data to determine its eicacy (DeVoe, 2008).
Similar indings have been reported with the addition of umbilical artery Doppler velocimetry in twins with concordant growth. For example, when umbilical artery Doppler velocime try was added to management compared with fetal testing based on fetal-growth parameters alone in the absence of growth dis cordance, perinatal outcomes were not improved (Giles, 2003).
Likewise, Hack and associates (2008) investigated the utility mortality rates using pulsatility indices of the umbilical artery.
tons, and data suggest that testing in multifetal gestations per forms no better. In cases of abnormal testing in one twin and normal results in another, iatrogenic preterm delivery remains a major concern. Options are similar to those described in the management of impending fetal death (p. 884).
Preterm labor is common in multifetal pregnancies and may complicate up to 50 percent of twin, 75 percent of triplet, and 90 percent of quadruplet pregnancies (Elliott, 2007). Similar to singleton preterm labor, intraamnionic infection is docu mented in approximately one third of twin pregnancy cases (Oh,r2017).
In twins, the proportion of preterm births varies widely from 40 to 70 percent (Giufre, 2012). For example, black women have disparately higher risks for preterm delivery (Grant, 2017).
• Prediction of Preterm Birth