Dizygotic twinning, birth order, female psychology, and coital rates.
D001722:Birth Order; D003075:Coitus; D005260:Female; D005298:Fertility; D006801:Humans; D007231:Infant, Newborn; D008393:Marriage; D010060:Ovulation; D011247:Pregnancy; D012306:Risk; D012725:Sexual Behavior; D014427:Twins; D014429:Twins, Dizygotic