2ND-TRIMESTER MATERNAL SERUM SCREENING USING ALPHA-FETOPROTEIN, HUMANCHORIONIC-GONADOTROPIN, AND UNCONJUGATED ESTRIOL - EXPERIENCE OF A REGIONAL PROGRAM

Over a 2-year period from January 1991 to December 1992, second-trimes ter maternal serum screening for Down's syndrome using alpha-fetoprote in (alphaFP), human chorionic gonadotrophin (hCG), and unconjugated oe striol (uE3) was made available to five health districts in East Angli a, with a total population of 1.2 million. Amniocentesis was offered w hen the risk of Down's syndrome at term was 1:200 or greater. 25 359 s ingleton pregnancies were screened, representing an uptake of 77 per c ent. The recall rate for the 24 per cent of women who had not had a da ting scan prior to the test was 9.4 per cent compared with 3.9 per cen t for those who had been scanned (P<0.0005). Seventy-five per cent (36 /48) of Down's syndrome pregnancies were detected for a false-positive rate of 4.0 per cent. Twenty-five out of 36 of detected Down's syndro me pregnancies were dated by scan prior to sampling, and in the 11 rem aining cases, the dates were confirmed by scan after a high-risk resul t was obtained. The exclusion of uE3 from the screening protocol would have reduced the detection rate to 52 per cent (25/48) for the same f alse-positive rate. Eighty-five per cent of women identified at high r isk accepted the offer of an amniocentesis. Other fetal abnormalities detected were trisomy 18 (3), trisomy 13 (2), 45,X (6), 69,XXX (5), ot her chromosome abnormalities (9), open neural tube defects (26), hydro cephalus (7), abdominal wall defects (4), and steroid sulphatase defic iency (6).