Sex ratios in neural tube defects.
D000757:Anencephaly / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D009436:Neural Tube Defects / Q000453:epidemiology*; D011247:Pregnancy; D012744:Sex Ratio; D016136:Spina Bifida Occulta / Q000453:epidemiology