title: Letter: Anencephaly, spina bifida, dizygotic twinning, and hormones.
mesh_terms: D000757:Anencephaly / Q000175:diagnosis / Q000235:genetics*; D004200:Diseases in Twins; D005260:Female; D006062:Gonadotropins / Q000097:blood; D006579:Heterozygote; D006801:Humans; D011247:Pregnancy; D011258:Pregnancy Tests; D011296:Prenatal Diagnosis; D016135:Spinal Dysraphism / Q000175:diagnosis / Q000235:genetics*
chemical_list: D006062:Gonadotropins