title: Major central nervous system malformations in South Wales. II. Pregnancy factors, seasonal variation, and social class effects.
mesh_terms: D000757:Anencephaly / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005494:Folic Acid Deficiency / Q000150:complications; D006801:Humans; D006849:Hydrocephalus / Q000453:epidemiology / Q000209:etiology*; D007231:Infant, Newborn; D007251:Influenza, Human / Q000150:complications; D008297:Male; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious; D012621:Seasons; D012923:Social Class; D016135:Spinal Dysraphism / Q000453:epidemiology / Q000209:etiology*; D014852:Wales