Outcome of twin gestations following sonographic demonstration of two heart beats in the first trimester.

We conducted a prospective study to assess pregnancy outcome following a first-trimester ultrasound examination demonstrating intrauterine twins with heart beats. Our study population included 68 cases of twin gestations in which a first-trimester scan demonstrated two heart beats. We correlated pregnancy outcome with placentation type, gestational age, maternal age, and method of conception. There were 59 dichorionic and nine monochorionic gestations. Twenty-six of the dichorionic pregnancies resulted from treatment for infertility. Among all 68 cases, 54 (79%) delivered viable twins, eight (12%) delivered one infant, and six (9%) delivered none. The outcome in dichorionic gestations (83% delivered twins, 12% singletons, 5% none) was significantly better than in monochorionic gestations (56%, 11%, 33%, respectively) (p < 0.05). Among dichorionic twins, pregnancy outcome was worse in twins initially identified on a 6-7.9 week ultrasound examination (74% delivered twins, 21% singletons, 6% none) as compared to those identified at 8-13 weeks (96%, 0%, 4%, respectively) (p < 0.05). The outcome in dichorionic gestations was worse in women over 35 compared to those under 35 (p < 0.05), and those with treatment for infertility compared to those who conceived naturally (p = 0.05). These results provide prognostic information about outcome of twin pregnancies scanned in the first trimester as a function of chorionicity, gestational age, maternal age, and method of conception.