title: Twins and neural tube defects.
mesh_terms: D000014:Abnormalities, Drug-Induced; D000757:Anencephaly / Q000139:chemically induced / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D002996:Clomiphene / Q000009:adverse effects; D004200:Diseases in Twins; D004739:England; D005260:Female; D005787:Gene Frequency; D006801:Humans; D007231:Infant, Newborn; D007494:Ireland; D007564:Japan; D008297:Male; D008423:Maternal Age; D008954:Models, Biological; D011247:Pregnancy; D012606:Scotland; D012621:Seasons; D012737:Sex Factors; D012744:Sex Ratio; D012923:Social Class; D016135:Spinal Dysraphism / Q000453:epidemiology; D014852:Wales
chemical_list: D002996:Clomiphene