[The biparietal fetal diameter during twin and normal pregnancy. An ultrasonographic comparison (author's transl)]

The growth of the fetal biparietal diameter (BPD) of twins is compared with the BPD of the normal pregnancy during gestation. Until 26th week of gestation the growth curves of both groups are nearly identic. From the 28th week onwards the growth of the twins' BPD is remarkably less than in normal pregnancies. The difference in the 40th week is about 10 mm, it is statistically highly significant. In pregnancies of unknown duration the BPD should be measured early, i.e. before 28th-30th week with a control 4 weeks later. No twin pregnancy lasted until the 280th day post menstruationem. So in twin pregnancies the day of delivery should be determined to an earlier date, i.e. ca the 27th day post menstruationem.