Anencephaly and twinning.
D009008:Abnormalities, Severe Teratoid; D000757:Anencephaly / Q000235:genetics; D002877:Chromosomes, Human; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D011247:Pregnancy; D014427:Twins