<prompt> Incidence of Downs syndrome is directly proportional toParityConsanguinityMaternal ageMutations  <response>: Ans. c Maternal age. Ref. Harrison, Internal Medicine, 16th ed., 383The incidence of Down ys syndrome is highly correlated to maternal age.QUADRUPLE TEST FOR DOWNS SYNDROME AFP beta-HCG Unconjugated estriol Human placental lactogenplacental protein A 