A PROSPECTIVE TRIAL OF PRENATAL SCREENING FOR DOWN-SYNDROME BY MEANS OF MATERNAL SERUM ALPHA-FETOPROTEIN, HUMAN CHORIONIC-GONADOTROPIN, ANDUNCONJUGATED ESTRIOL

OBJECTIVE: Our purpose was to prospectively evaluate the effectiveness of prenatal screening for Down syndrome by means of multiple serum ma rkers. STUDY DESIGN: Alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol were measured in 8233 midtrimester serum samp les, including 7492 from women < 35 years old and 741 from women great er-than-or-equal-to 35 years old. Down syndrome risks were computed by means of age and all three markers. Further testing was recommended f or patients with a risk greater-than-or-equal-to 1:270. Testing for tr isomy 18 was recommended for patients with an alpha-fetoprotein less-t han-or-equal-to 0.70 multiples of the median, human chorionic gonadotr opin less-than-or-equal-to 0.50 multiples of the median, and unconjuga ted estriol less-than-or-equal-to 0.55 multiples of the median. RESULT S: Of women screened initially 10.4% had a Down syndrome risk greater- than-or-equal-to 1:270; 10 of 12 known cases of Down syndrome were ide ntified. One abnormality was detected for every 33 amniocenteses perfo rmed in this group. Of 0.4% of patients at increased risk for trisomy 18, two cases of trisomy 18 and one of triploidy were found. CONCLUSIO N: Multiple marker screening is effective in identifying the majority of fetal chromosome anomalies.