Growth pattern of twins of different chorionicity evaluated by sonographicbiometry

Objective: To determine differences between growth patterns of monochorioni c and dichorionic twins, and of concordant and discordant twins of both cho rionicities. Methods: We studied 70 cases of concordant twins (24 monochorionic, 46 dich orionic) and 45 cases of discordant twins (25 monochorionic, 20 dichorionic ). In each case, growth was measured longitudinally by ultrasound biometry and the growth pattern was depicted. Results: There were no differences in incremental growth between concordant monochorionic and dichorionic twins. The growth curve of concordant twins of both chorionicities was almost the same as that of a singleton until 34 weeks' gestation. However, in the discordant twins, the growth of the large r twin matched the growth curve of a singleton or concordant twin, but the growth of the smaller twin gradually decreased to the range of growth restr iction The growth curves for monochorionic discordant twins appeared to be representative of two groups, one of which had onset of discordancy before 24 weeks. Conclusion: it is clinically important to determine chorionicity early in t win pregnancies, to calculate the percentage of discordancy between the fet uses, and to examine longitudinal fetal growth curves in each chorionicity. (Obstet Gynecol 2000;95:656-61. (C) 2000 by The American College of Obstet ricians and Gynecologists.).