If discordancy is identiied in a monochorionic twin pregnancy, umbilical artery Doppler studies in the smaller fetus may help guide management (Gratac6s, 2007). Namely, investigators have correlated umbilical artery Doppler results with placental indings and with the degree of selective fetal-growth restriction to predict fetal outcome (Gratac6s, 2012). hese correlations have yielded categories of selective fetal-growth restriction. Type I is characterized by positive end-diastolic low, a smaller degree of weight discordance, and a relatively benign clinical course. Type II displays persistently absent end-diastolic flow in the smaller twin and carries a high risk of deterioration and demise. Type III is intermittently absent or reversed end-diastolic flow. Because of large artery-to-artery anastomoses associated with the placentas in this category, type III is associated with a lower risk of deterioration than type II. In all evaluated cases, unequally shared placenta was noted to some degree.
With uncomplicated dichorionic multifetal gestations, use of antepartum surveillance has not improved perinatal outcomes. In sum, the American College of Obstetricians and Gynecologists (2016) recommends that antepartum testing be performed in multi fe tal gestations for indications similar to those for singleton fetuses (Chap. 17, p. 331).
At Parkland, all women with twin discordancy :25 percent undergo daily monitoring as an inpatient. Data are limited to establish the optimal timing of delivery of twins for size discordancy alone. For those at advanced gestational ages, delivery can be pursued.
• Death of One Fetus
At any time during multifetal pregnancy, one or more fetuses may die, either simultaneously or sequentially. Causes and incidence of fetal death are related to zygosity, chorionicity, and growth concordance.
In some pregnancies, one fetus dies remote from term, but pregnancy continues with one or more live fetuses. When this occurs early in pregnancy, it may manifest as a vanishing twin, discussed on page 871. In a slightly more advanced pressed against the fetal membranes. Anatomical parts can be identified as marked. Demise of this twin had been noted during sonographic examination performed at 17 weeks' gestation. Its viable cotwin delivered at 40 weeks. (Used with permission from
Dr. Michael V. Zaretsky.) gestation, fetal death may go undetected until delivery. In this case, delivery ofa normal newborn is followed by expulsion of a dead fetus that is barely identiiable. It may be compressed appreciably-'tus compressus, or it may be lattened remarkably through desiccation-'tuspapyraceus (Fig. 45-24).
As shown in Figure 45-25, the risk ofstillbirth is related to gestational age in all twins but is much higher for monochorionic twin pregnancies before 32 weeks' gestation. In a review of 9822 twin pregnancies, Morikawa and associates (2012) reported that 2.5 percent of monochorionic diamnionic twins �o 0: .� 15 ..0
FIGURE 45-25 Prospective risk of stillbirth among women who reached a given gestational week (per 1000 women). (Reproduced with permission from Morikawa M, Yamada 1, Yamada T, et al: Prospective risk of stillbirth: monochorionic diamniotic twins vs dichorionic twins, J Perinat Med. 2012 Jan 10;40(3):245-249.) greater than 22 weeks had a death of one or both twins. This compared with 1.2 percent of dichorionic twins. In this same review, women with monochorionic diamnionic twins who lost one twin were 16 times more likely to experience death of the cotwin than women with dichorionic twins who lost one twin.