Ultrasound in twin pregnancy.

This review evaluates the role of ultrasound in twin gestation. Ultrasound is essential in the diagnosis and management of perinatal complications common in twins, including fetal anomalies, conjoined twins, acardiac twinning, fetal demise, prematurity, intrauterine growth retardation, and twin-to-twin transfusion. Indications for first-trimester scanning are reviewed, as well as its use in determining type of placentation, chorionicity, and amnionicity. The focus of this article will be the use of ultrasound and Doppler velocimetry in the evaluation of fetal growth and subsequent management of intrauterine growth retardation in twins, as well as the value of real-time ultrasound and Doppler evaluation in the diagnosis of discordant growth and twin-to-twin transfusion syndrome.