Maternal serum levels of dimeric inhibin A in pregnancies affected by trisomy 21 in the first trimester

Dimeric inhibin A was measured in maternal serum samples from 45 pregnancie s affected by trisomy 21 and 493 samples from unaffected pregnancies at 10- 14 weeks of gestation. Inhibin A levels in affected pregnancies were compar ed with levels of free beta -hCG and PAPP-A in the same series. In the tris omy 21 group, the median multiple of the median (MoM) inhibin A was not sig nificantly elevated (1.28 vs 1.00) with only 15.5% being above the 95th cen tile. In contrast, the median MoM free beta -hCG was significantly increase d (1.05 vs 1.00) with 36% above the 95th centile and PAPP-A was significant ly reduced (0.49 vs 1.00) with 42% below the 5th centile. Inhibin A levels in the trisomy 21 group were significantly correlated with gestational age such that median levels rose from 1.04 at 11 weeks to 1.30 at 12 weeks and 1.67 at 13 weeks. These findings suggest that first trimester biochemical s creening for trisomy 21, which is currently optimised using maternal serum free beta -hCG and PAPP-A and fetal nuchal translucency, will not benefit f rom the inclusion of inhibin A. Copyright (C) 2001 John Wiley & Sons, Ltd.