Ethnic differences in twinning rates in Nigeria.
D005006:Ethnicity; D005260:Female; D005306:Fertilization; D005828:Genetics, Population; D006801:Humans; D008423:Maternal Age; D009549:Nigeria; D010060:Ovulation; D010063:Ovum; D010298:Parity; D011247:Pregnancy; D014427:Twins