Prenatal diagnosis of trisomy 18 and trisomy 21 in a population of patients as screen positive

Objective: In order to study the chromosome abnormalities in women receiving prenatal chromosome analysis after a Down syndrome or Edward′s syndrome screen-positive result by maternal serum during the second trimester.Methods:The levels of maternal serum alpha-fetoprotein(AFP),Free beta human chorionis gonadotropin(Free-hcG β) in 54580 patients were measured by PE TRFIA.By use of a 1:270 midtrimester Down′s syndrome risk,a 1:350 midtrimester edwards syndrome risk cut off value,Amniotic fluid were cultured in wimen with positive results in serum screening.Results: 2615 patients were screen positive for trisomy 18 or trisomy 21,corrected screen-positive rate 4.79%(2615/54580).Karyotypes were reviewed for 1161(44.4%,1161/2615) of these patients who received prenatal chromosome analysis.In addition to 14 cases of Down′s syndrome,5 cases Edwards syndrome and 3 cases sex chromosome,7 other fetal chromosome abnormality were found among the 1161 pregnant women(2.49%,29/1161).Conclusion:Peramniocentesis counseling for patients with positive screening results should reflect the relatively high probability that an abnormality other than chromosome abnormalities maybe identified.So prenatal screening for maternal serum markers is effective in detecting foetus chromosome abnormalities.