Maternal age, parity, and twin pregnancies.
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."
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007194:India; D007231:Infant, Newborn; D008423:Maternal Age; D010298:Parity; D011247:Pregnancy; D011272:Pregnancy, Multiple; D012959:Socioeconomic Factors; D014427:Twins