Gestation and Birthweight in Dizygotic Twins: Girls Call the Tune

In: Twin research and human genetics: the official journal of the International Society for Twin Studies (ISTS) and the Human Genetics Society of Australasia, Band 10, Heft S1, S. 6-7

Abstract

AbstractUnlike-sex twins provide a unique natural experiment to investigate the influence of sex on gestation. Our data showed that length of gestation of unlike-sex pairs is similar to that of female same-sex pairs, and significantly (0.4 wks,p= .02) longer than that of male same-sex pairs. Birthweight of female unlike-sex twins was similar to female same-sex twins, but male unlike-sex twins weighed 78 g more than male same-sex twins (p= .001). These data show that in unlikesex pairs it is the girl that prolongs gestation for her brother, resulting in a higher birthweight than that of same-sex boys.