The risk of a structural congenital cardiac anomaly in at least 1 of an MC MA twin pair is 8 times that of a MC diamniotic twin pair [9]. In addition, if 1 MC twin is affected, the risk of the co-twin having a cardiac anomaly is higher. For these reasons, fetal echocardiography should be considered in MC gestations [9]. US Pregnant Uterus Biophysical Profile BPP is performed in late second and third trimesters. There is no role for BPP at the time of second trimester anatomy scan. Placental cord insertion of each twin should be documented in the second trimester. Marginal or velamentous cord insertion are common among MC pregnancies, with velamentous cord insertion present in up to 22% of MC twins [54]. Velamentous cord insertion in MC twins increases the risk of adverse outcome, including small for gestational age and sFGR, lower gestational age at birth, and intrauterine fetal demise [55]. There is also a higher frequency of vasa previa when a velamentous cord insertion is found, especially in MC pregnancies [49]. Velamentous cord insertion in 1 or both twins is associated with increased risk of TTTS, and the risk of discordant growth is determined by both discordance in insertion sites and velamentous cord insertion in 1 twin [56,57]. In a study by Saito et al [57], 27% of twin pairs with abnormal cord insertions (defined as twin pair with velamentous cord insertions and/or marginal cord insertion in 1 or both twins) developed TTTS compared with 7% of twin pairs with normal cord insertions in both. If prior history of cesarean delivery or uterine instrumentation is present, assessment for placenta accreta spectrum can be performed. US Pregnant Uterus Transvaginal Transvaginal examination of the pregnant uterus and cervix can be performed as an adjunct for limited transabdominal fetal evaluation. Additional indications include assessment of the cervix and placenta and detection of vasa previa.
Multiple Gestations. The risk of a structural congenital cardiac anomaly in at least 1 of an MC MA twin pair is 8 times that of a MC diamniotic twin pair [9]. In addition, if 1 MC twin is affected, the risk of the co-twin having a cardiac anomaly is higher. For these reasons, fetal echocardiography should be considered in MC gestations [9]. US Pregnant Uterus Biophysical Profile BPP is performed in late second and third trimesters. There is no role for BPP at the time of second trimester anatomy scan. Placental cord insertion of each twin should be documented in the second trimester. Marginal or velamentous cord insertion are common among MC pregnancies, with velamentous cord insertion present in up to 22% of MC twins [54]. Velamentous cord insertion in MC twins increases the risk of adverse outcome, including small for gestational age and sFGR, lower gestational age at birth, and intrauterine fetal demise [55]. There is also a higher frequency of vasa previa when a velamentous cord insertion is found, especially in MC pregnancies [49]. Velamentous cord insertion in 1 or both twins is associated with increased risk of TTTS, and the risk of discordant growth is determined by both discordance in insertion sites and velamentous cord insertion in 1 twin [56,57]. In a study by Saito et al [57], 27% of twin pairs with abnormal cord insertions (defined as twin pair with velamentous cord insertions and/or marginal cord insertion in 1 or both twins) developed TTTS compared with 7% of twin pairs with normal cord insertions in both. If prior history of cesarean delivery or uterine instrumentation is present, assessment for placenta accreta spectrum can be performed. US Pregnant Uterus Transvaginal Transvaginal examination of the pregnant uterus and cervix can be performed as an adjunct for limited transabdominal fetal evaluation. Additional indications include assessment of the cervix and placenta and detection of vasa previa.