ZYGOSITY AND INTRAUTERINE GROWTH OF TWINS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 55  (6) , 684-687
Abstract
Sonar measurements of fetal biparietal diameter (BPD) [678] were used to assess the intrauterine growth of 182 twins between 18 and 40 wk gestation. These values, and weight and body length at birth, were related to zygosity, which was determined by sex of the infants, histologic examination of placenta or blood grouping. Mean BPD of twin 1 was larger than that of twin 2 in monozygotic and dizygotic pairs throughout the study period (P < 0.001). BPD size of the dizygotic infants exceeded that of the monozygotic among twins 1 (P < 0.001) and twins 2 (P < 0.001). Absolute intrapair differences of birth length and weight were larger among dizygotic than among monozygotic twins. Apparently in late pregnancy a substantial 1-way intertwin intrasfusion among monochorial twins does not occur frequently enough to mask the inherent genetically determined similarity between the twins. The appearance already in the 2nd trimester of the differences in the longitudinally monitored BPD between monozygotic and dizygotic twins suggests that the discrepancy is determined early in gestation.

This publication has 3 references indexed in Scilit: