Beiguelman B, Franchi-Pinto C, Dal Colletto G M, Krieger H
Department of Medical Genetics, School of Medicine, UNICAMP, Campinas, SP, Brazil.
Acta Genet Med Gemellol (Roma). 1995;44(3-4):163-8. doi: 10.1017/s0001566000001574.
The annual variation of the sex ratio (SR) of 1385 twin births was analyzed and compared to that of 85909 singletons. These births referred not only to live births but also to stillbirths in two southeastern Brazilian maternity hospitals from 1984 to 1993. While the annual variation of the SR of singletons was very small, that of twin births was extremely high, due to the significant heterogeneity of the annual data. It is suggested that the large SR annual variation of the twin birth might be a consequence of the variation of male or female monozygotic twins. The hypothesis that twin births show a lower sex ratio than singletons could be supported by the present data.
分析了1385例双胎分娩的性别比（SR）的年度变化，并与85909例单胎分娩的性别比进行了比较。这些分娩不仅包括活产，还包括1984年至1993年巴西东南部两家妇产医院的死产。虽然单胎分娩的SR年度变化非常小，但由于年度数据的显著异质性，双胎分娩的SR年度变化极高。有人认为，双胎分娩的SR年度变化较大可能是男性或女性单卵双胞胎变化的结果。双胎分娩的性别比低于单胎分娩这一假设可以得到目前数据的支持。
