TVUS imaging is routinely performed in some institutions or can be done as needed, when the transabdominal evaluation is considered incomplete or suboptimal. If prior history of cesarean delivery or uterine instrumentation is present, assessment for placenta accreta spectrum can be performed. MRI Fetal Without and With IV Contrast MRI fetal without and with IV contrast does not have a role in the second trimester anatomy evaluation. Gadolinium contrast is usually not administered for fetal indications. Multiple Gestations MRI Fetal Without IV Contrast MRI fetal without IV contrast does not have a role in the initial second trimester anatomy evaluation. MRI fetal without IV contrast can be considered for multiple gestations if an abnormality is noted in the second trimester anatomy US. It can also be considered when maternal factors, such as soft tissue attenuation, limit sonographic evaluation of the fetus. In all cases, anatomy evaluation with MRI without IV contrast is performed after an US examination has been performed. US Assessment for TTTS With very rare exceptions, DC twins with separate placentas do not develop TTTS or other complications associated with placental sharing and vascular connections. Hence, US assessment for TTTS is not useful for DC or multichorionic twins. US Duplex Doppler Fetal Middle Cerebral Artery US duplex Doppler fetal MCA is not useful for complications of multiple pregnancies at the second trimester anatomy scan. If there is a risk for fetal anemia or if hydrops is noted during evaluation, fetal MCA Doppler can be performed and interpreted using established nomograms [45]. US Duplex Doppler Fetal Umbilical Artery US duplex Doppler fetal UA is not useful for complications of multiple pregnancies at the second trimester anatomy scan. However, if growth restriction is noted during evaluation, fetal UA Doppler can be performed.
Multiple Gestations. TVUS imaging is routinely performed in some institutions or can be done as needed, when the transabdominal evaluation is considered incomplete or suboptimal. If prior history of cesarean delivery or uterine instrumentation is present, assessment for placenta accreta spectrum can be performed. MRI Fetal Without and With IV Contrast MRI fetal without and with IV contrast does not have a role in the second trimester anatomy evaluation. Gadolinium contrast is usually not administered for fetal indications. Multiple Gestations MRI Fetal Without IV Contrast MRI fetal without IV contrast does not have a role in the initial second trimester anatomy evaluation. MRI fetal without IV contrast can be considered for multiple gestations if an abnormality is noted in the second trimester anatomy US. It can also be considered when maternal factors, such as soft tissue attenuation, limit sonographic evaluation of the fetus. In all cases, anatomy evaluation with MRI without IV contrast is performed after an US examination has been performed. US Assessment for TTTS With very rare exceptions, DC twins with separate placentas do not develop TTTS or other complications associated with placental sharing and vascular connections. Hence, US assessment for TTTS is not useful for DC or multichorionic twins. US Duplex Doppler Fetal Middle Cerebral Artery US duplex Doppler fetal MCA is not useful for complications of multiple pregnancies at the second trimester anatomy scan. If there is a risk for fetal anemia or if hydrops is noted during evaluation, fetal MCA Doppler can be performed and interpreted using established nomograms [45]. US Duplex Doppler Fetal Umbilical Artery US duplex Doppler fetal UA is not useful for complications of multiple pregnancies at the second trimester anatomy scan. However, if growth restriction is noted during evaluation, fetal UA Doppler can be performed.