This diagnostic test is aimed to compare the Karyotyping, CMA and NIPT for prenatal diagnosing chromosomal anomalies. Pregnant women who needed prenatal genetic diagnosis meted the study criterion; fetal amniotic fluid was regular examined by Karyotyping and CMA, and maternal peripheral blood was collected for NIPT detecting. And the CMA result as a golden standard, the main outcome is compared the diagnostic efficacy of NIPT for diagnosing chromosomal anomalies.