High maternal serum inhibin A levels following the loss of one fetus in a twin pregnancy.

Inhibin A levels are elevated in the second trimester of pregnancies affected with fetal Down syndrome, on average, two times the level in unaffected pregnancies. Inhibin A levels are also two times higher in twin than in singleton pregnancies. Prenatal serum screening using inhibin A levels as a second trimester marker began at the Women and Infants Hospital in March 1998. We describe a case of a 17-year-old woman thought to have had a complete spontaneous abortion of a twin pregnancy but later found to be continuing the pregnancy with a single fetus. Routine second trimester prenatal serum screening revealed an extremely elevated inhibin A level of 39 MoM (multiples of the median). The patient delivered an apparently healthy female infant at 41 weeks of gestation. Therefore, inhibin A may be extremely elevated in the second trimester of a twin pregnancy after the loss of one fetus and this increased inhibin A level does not have any obvious adverse maternal or fetal effects.