title: Impact of ovarian stimulation on studies of twinning.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Berry
mesh_terms: D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D010062:Ovulation Induction; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D012042:Registries; D038522:Twinning, Monozygotic / Q000187:drug effects*; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D014815:Vitamins; D005492:Folic Acid