The first-trimester growth-discordant twin: An ominous prenatal finding

Objective: To evaluate the clinical significance and the natural course of discordant twin growth found during the first trimester of pregnancy. Methods: This was a retrospective survey between 1992–1993 of women presenting to the ultrasonographic unit with twin pregnancies in which considerable interfetal size variation was noted in the first trimester. Discordant embryonal growth was defined as a difference in crown-rump length corresponding to 5 or more days in the estimated gestational age. Only cases that presented with continued viability of both twins were reviewed. Cases were thoroughly followed by ultrasound examinations throughout pregnancy. Neonatal records provided the outcome data. Results: Five cases with first-trimester discordant twin growth were identified. All had complications of major congenital anomalies in the smaller twin, ie, diaphragmatic hernia, ventriculomegaly, schizencephaly, critical aortic atresia, and sacral agenesis. Conclusions: The first-trimester growth-discordant twin is at increased risk for congenital anomalies. Meticulous sonographic search for congenital anomalies is indicated when inter-twin size variation is evident in the first trimester. (Obstet Gynecol 1994;84:110-4).