title: Secular changes in dizygotic twinning rates.
mesh_terms: D000328:Adult; D003431:Cross-Cultural Comparison; D005060:Europe; D005260:Female; D005298:Fertility; D005306:Fertilization; D006801:Humans; D007564:Japan; D009520:New Zealand; D010063:Ovum; D011247:Pregnancy; D014427:Twins