产妇年龄、产次和双胎妊娠。

Prog Clin Biol Res. 1978;24 Pt B:99-103.

Significant effects of maternal age and parity on twinning were observed in a sample of 10,916 third trimester deliveries. Younger mothers exhibited low rates of twinning in low parities and higher rates in high parities. Older mothers exhibited high rates of twinning right from the low parities, with a declining rate after "parity 4."

在10916例孕晚期分娩样本中观察到母亲年龄和胎次对双胎妊娠有显著影响。年轻母亲在低胎次时双胎妊娠率较低，在高胎次时双胎妊娠率较高。年龄较大的母亲从低胎次开始双胎妊娠率就较高，在“第4胎次”之后双胎妊娠率呈下降趋势。