Goswami R, Goswami H K
Department of Genetics, University Campus, Bhopal, India.
Acta Genet Med Gemellol (Roma). 1993;42(3-4):289-94. doi: 10.1017/s0001566000003299.
Birth statistics (on 13,887.943 births) from 11 Indian States indicate a fall in the dizygotic twinning rate and a rise in the monozygotic twinning rate over the decade between 1982 and 1991. These figures seem to reverse the trend of the period 1960-1982. One plausible explanation is offered by the age-data on mothers, which indicate that twins of different sex are more frequently born to mothers above the age of 35. Since extensive family planning measures have reduced the upper age-limit of mothers, the birth-rate of twins of different sex has also fallen. Due to the increased proportion of twins of the same sex, Weinberg's differential method will therefore report a decline in the dizygotic twinning rate, wherever the mean age of mothers has fallen (i.e. most mothers do not reproduce after the age of 35).
来自印度11个邦的出生统计数据（基于13887943例出生情况）表明，在1982年至1991年这十年间，双卵双胎率下降，单卵双胎率上升。这些数据似乎扭转了1960年至1982年期间的趋势。母亲的年龄数据提供了一种合理的解释，该数据表明，35岁以上母亲生育不同性别的双胞胎更为频繁。由于广泛的计划生育措施降低了母亲的最高年龄限制，不同性别的双胞胎出生率也有所下降。由于同性双胞胎的比例增加，因此，无论母亲的平均年龄在何处下降（即大多数母亲在35岁之后不再生育），温伯格差异法都会显示双卵双胎率下降。
