title: Has fecundability been declining in recent years in developed countries?
mesh_terms: D001723:Birth Rate; D003075:Coitus; D005260:Female; D005298:Fertility; D006801:Humans; D007246:Infertility / Q000453:epidemiology; D008297:Male; D011247:Pregnancy; D013076:Sperm Count; D014429:Twins, Dizygotic