Letter: Prospective data on risk of Down syndrome in relation to maternal age.
D000328:Adult; D000649:Amniocentesis; D004314:Down Syndrome / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D011247:Pregnancy; D012306:Risk