Antepartum management of twin gestation: ultrasound.

1. The use of ultrasound may improve perinatal outcome in twin pregnancy. 2. Singleton growth curves for FL, BPD, and AC may be used to assess fetal growth prior to 28 weeks gestation. 3. After 28 weeks gestation, specific twin growth curves should be used. However, increased morbidity may be seen when fetal weight falls from the normal singleton predictive curves. 4. Amnionicity and chorionicity frequently can be determined. This should be attempted early in the second trimester so that appropriate monitoring can be offered for the monoamnionic and monochorionic gestations. 5. Serial assessment of fetal growth should be performed. In the authors' institutions, growth scans are performed in twins every 2 weeks after 24 weeks gestation. 6. Evidence on ultrasound examination of discordant growth suggests either fetal growth retardation or TTS. In the presence of a dichorionic placentation, growth retardation of one twin is the usual diagnosis. If placentation is monochorionic, it is difficult to differentiate between growth retardation and TTS. The presence of polyhydramnios, a stuck twin, or fetal hydrops are suggestive of TTS. 7. The value and safety of cordocentesis and the management of twin pregnancy and diagnosis of TTS have not been established. 8. Doppler ultrasound may be useful in the assessment of the IUGR twin fetus. The use of Doppler in the identification of TTS is not yet clear.