Dimeric inhibin A as a marker for Down's syndrome in early pregnancy

Adding a screen for maternal blood levels of inhibin A to the measurement of alpha fetoprotein and human chorionic gonadotropin could increase the detection of Down syndrome during the second trimester of pregnancy. Inhibin is a protein produced by the placenta that contains an alpha subunit and two beta subunits, A or B. Researchers took blood samples from 58 women whose fetuses were known to have Down syndrome, 32 whose fetuses were affected with trisomy 18 and 438 who had normal fetuses. Blood levels of inhibin A in women with Down syndrome fetuses were similar to those in women with normal fetuses between 7 and 11 weeks gestation, but rose to twice the median value by 15 to 18 weeks. Adding a screen for inhibin A blood levels to a screen that included age and alpha fetoprotein and human chorionic gonadotropin levels increased the detection rate of Down syndrome to 75%, compared to 53% when age, alpha fetoprotein and human chorionic gonadotropin alone were used.