Congenital malformations in twins

Background: A higher prevalence of congenital malformations among twins tha n among single has been reported in the literature. Aim: To study the incid ence of congenital malformations in twins in the maternity hospital of the University of Chile in the period 1983-1997. Material and methods: As part of the Latin American Collaborative Study of Congenital Malformations, ever y newborn in the maternity hospital was examined by a neonatologist and con genital malformations were recorded in a special file. Results: In the stud y period there were 48.663 deliveries of single pregnancies and 448 deliver ies of twin pregnancies, giving birth to 886 twins born alive and 17 stillb irths (1.9% mortality). Of these, there were 423 twins, 17 triplets, a sext uple delivery and two siamese. Seven point one percent of twins born alive and 6.5% of single newborns had a congenital malformation. The prevalence o f malformations in twins and single stillbirths was 35.2 and 17.2% respecti vely (p < 0.04). In four pairs and siamese newborns, malformations typical of monozygotic twins were present, such as an acardiac fetus with Trap sequ ence, a papyraceous fetus and two with hydroanencephaly. Twelve twins had m alformations attributable to uterine compression. Conclusions: this study d id not find a higher frequency of malformations comparing twins with single babies born alive, but in stillbirths there was a significant difference b etween single and twin stillbirths (7.1% versus 35.2% respectively, p < 0.0 5.