Excess twinning in the parents of spina bifida.
D004200:Diseases in Twins / Q000235:genetics*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011272:Pregnancy, Multiple; D016136:Spina Bifida Occulta / Q000235:genetics*