In 18 pregnant women aged over 35 years,1 (5.56%) with trisomy 21 was detected, and 3 of trisomy 21 were in 229 pregnant women aged under 35 years (1.31%,P=0.235).

• 高龄孕妇中 2 1三体检出率为 5 .；5 6%25 (1/ 18)；非高龄组为 1