title: The parity effect and fertility in mothers of twins.
mesh_terms: D000293:Adolescent; D000328:Adult; D001722:Birth Order; D005260:Female; D005298:Fertility; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008423:Maternal Age; D010298:Parity; D011247:Pregnancy; D011272:Pregnancy, Multiple; D011446:Prospective Studies; D013223:Statistics as Topic; D014427:Twins; D014481:United States