A prospective trial of prenatal screening for Down syndrome by means of maternal serum alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol.

Abstract

Our purpose was to prospectively evaluate the effectiveness of prenatal screening for Down syndrome by means of multiple serum markers. alpha-Fetoprotein, human chorionic gonadotropin, and unconjugated estriol were measured in 8233 midtrimester serum samples, including 7492 from women < 35 years old and 741 from women > or = 35 years old. Down syndrome risks were computed by means of age and all three markers. Further testing was recommended for patients with a risk > or = 1:270. Testing for trisomy 18 was recommended for patients with an alpha-fetoprotein < or = 0.70 multiples of the median, human chorionic gonadotropin < or = 0.50 multiples of the median, and unconjugated estriol < or = 0.55 multiples of the median. Of women screened initially 10.4% had a Down syndrome risk > or = 1:270; 10 of 12 known cases of Down syndrome were identified. One abnormality was detected for every 33 amniocenteses performed 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. Multiple marker screening is effective in identifying the majority of fetal chromosome anomalies.