First‐trimester maternal serum human chorionic gonadotrophin as a marker for fetal chromosomal disorders

Abstract

The Dutch Working Party on Prenatal Diagnosis has initiated a study on the possibilities of first‐trimester screening for fetal chromosomal disorders. We report on maternal serum human chorionic gonadotrophin (MS‐hCG) measurements in 1348 pregnancies with a chromosomally normal fetus and 53 pregnancies with a chromosomally abnormal fetus. The median MS‐hCG concentration in 24 pregnancies with Down's syndrome was 1.19 multiples of the normal median (MoM). The MS‐hCG distributions in normal and Down's syndrome pregnancies did not differ significantly (t‐test: t = 1.945, p >0.05). We also found no difference between normal pregnancies and pregnancies with other chromosomal disorders (six cases of trisomy 18, MoM = 0.80; four cases of sex chromosome abnormality, MoM = 1.01; 17 cases of chromosomal mosaicism in chorionic villi, MoM = 1.11). Selecting an upper limit at the 90th centile could detect 25 per cent of pregnancies with Down's syndrome. We conclude that, in the first trimester, MS‐hCG as a screening factor for Down's syndrome is of minor value. However, MS‐hCG could be a useful factor in a first‐trimester screening programme based on a combination of markers.