A survey of twin pregnancy.
D000293:Adolescent; D000328:Adult; D001724:Birth Weight; D005260:Female; D006801:Humans; D007226:Infant Mortality; D007494:Ireland; D008297:Male; D008423:Maternal Age; D010298:Parity; D011247:Pregnancy; D011248:Pregnancy Complications; D011272:Pregnancy, Multiple; D013997:Time Factors; D014427:Twins