A definitive diagnosis of a multiple gestation can be made sonographically from 6 weeks gestation on by visualizing two or more fetuses with heartbeats. When a multiple gestation is identified, sonographic evaluation of the pregnancy is more than a series of singleton examinations. In addition to the evaluation of each fetus on its own, the fetal sizes and amniotic fluid volumes should be compared, and the pregnancy must be evaluated for placentation type and for the complications unique to multiple gestations. Invasive procedures requiring ultrasound guidance are more complicated than in singleton pregnancies because of the presence of multiple fetuses and amniotic cavities.