Periconceptional use of multivitamins and the occurrence of anencephaly and spina bifida.
D000757:Anencephaly / Q000453:epidemiology; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D009436:Neural Tube Defects / Q000453:epidemiology*; D011247:Pregnancy; D016136:Spina Bifida Occulta / Q000453:epidemiology; D014481:United States; D014815:Vitamins / Q000008:administration & dosage*
D014815:Vitamins