[Serum screening of fetal chromosome abnormality during second pregnancy trimester: results of 26,803 pregnant women in Jiangsu Province].

OBJECTIVE: To evaluate the efficiency of the second trimester screening for fetal chromosomal anomaly using maternal serum marker.
METHOD: 27,313 pregnant women with the gestational age of 15 - 20 weeks were selected by stratified combined with cluster sampling from 13 counties over Jiangsu province and 5 townships, towns, or subdistricts from 6 randomly selected cities from southern, central, and northern Jiangsu, totally 95 communities, between July 2002 and November 2006. Questionnaire survey was conducted. Body weight was taken. Ultrasonography was used to confirm the gestational age. Peripheral blood samples were collected to detect the maternal serum alpha-fetoprotein (AFP) and free beta human chorionic gonadotrophin (f-betaHCG). The risk values of Down syndrome and Edwards syndrome were calculated. The women at high risk of Down syndrome and Edwards syndrome for their fetuses were recommended to receive genetic counseling and amniocentesis. All babies were followed up until six months to four years of age after birth.
RESULTS: 26,803 of the 27,313 women (98%) were screened. The average was 25.1, and 1.7% of them were over 35. Serum screening showed that 1,244 (5%) were Down syndrome positive and 105 (0.4%) were Edwards syndrome positive. The final pregnant outcomes showed that 20 cases presented chromosomal abnormalities, of which 9 cases suffered from Down syndrome, 5 cases Edwards syndrome, and 6 cases other chromosomal abnormalities. The detection rate of Down syndrome and Edwards syndrome were 56% and 80% respectively.
CONCLUSION: Under good quality control high prenatal detection rate of fetal chromosomal abnormalities can be reached by screening of maternal serum AFP and f-betaHCG during the second pregnancy trimester. Good cost-effectiveness depends on the incidence of targeted birth defects.