Human sexual behaviour, delayed fertilization and Down's syndrome.
D000293:Adolescent; D000328:Adult; D002875:Chromosomes; D003075:Coitus; D004314:Down Syndrome / Q000209:etiology*; D005260:Female; D005306:Fertilization; D006801:Humans; D008297:Male; D008393:Marriage; D008423:Maternal Age; D008540:Meiosis; D008875:Middle Aged; D008954:Models, Biological; D008962:Models, Theoretical; D011336:Probability; D012725:Sexual Behavior; D013997:Time Factors