Mongolism, delayed fertilization and sexual behaviour.
D001699:Biometry; D003075:Coitus; D004314:Down Syndrome / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005306:Fertilization; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D010063:Ovum / Q000502:physiology*; D011247:Pregnancy; D011336:Probability