The recent decline in prevalence of anencephaly and spina bifida.
D000757:Anencephaly / Q000453:epidemiology*; D005006:Ethnicity; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008404:Massachusetts; D009790:Occupations; D010298:Parity; D011247:Pregnancy; D012189:Retrospective Studies; D012621:Seasons; D016135:Spinal Dysraphism / Q000453:epidemiology*