Tong S, Short R V
Department of Physiology, Monash University, Melbourne, Australia.
Hum Reprod. 1998 Jan;13(1):95-8. doi: 10.1093/humrep/13.1.95.
There is widespread concern about a possible decline in human fertility in recent decades. The spontaneous dizygotic twinning rate provides a way of measuring a combination of male plus female fertility as it reflects the frequency of double ovulation, the probability of fertilization, and the survival of the zygote. There was a decline in dizygotic twinning rates in developed countries which began around 1960 and continued until the late 1970s. The exact cause of the fall remains unknown. We suggest that it could have been due to a depression in the twin ovulation rate in women who stopped taking the oral contraceptive pill. The rise in the dizygotic twinning rates which occurred from the 1980s onwards in developed countries is almost certainly due to increasing use of ovulation-inducing agents, but this rise may have masked a continuing decline in dizygotic twinning. Monozygotic twinning rates have remained remarkably constant or increased only very slightly in recent decades. This makes it possible to use the dizygotic:monozygotic twinning ratio to monitor dizygotic twinning in populations where true incidence rates cannot be calculated, e.g. in hospitals where there may be selective referral of twins.
近几十年来，人们普遍担心人类生育率可能下降。自发双卵双胎率提供了一种衡量男性和女性生育能力综合情况的方法，因为它反映了双排卵的频率、受精的概率以及受精卵的存活率。发达国家的双卵双胎率在1960年左右开始下降，并持续到20世纪70年代末。下降的确切原因尚不清楚。我们认为，这可能是由于停止服用口服避孕药的女性双排卵率降低所致。发达国家从20世纪80年代起双卵双胎率的上升几乎肯定是由于促排卵药物使用增加，但这种上升可能掩盖了双卵双胎率的持续下降。近几十年来，单卵双胎率一直保持相当稳定，或仅略有上升。这使得在无法计算真实发病率的人群中，例如在可能存在双胞胎选择性转诊的医院中，可以使用双卵双胎与单卵双胎的比例来监测双卵双胎情况。
