Letter: Maternal age of dizygotic twins, superfecundation, and coital-rate.
D000293:Adolescent; D000328:Adult; D003075:Coitus; D005260:Female; D005306:Fertilization; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D012733:Sex Differentiation; D014427:Twins; D014429:Twins, Dizygotic