Serum concentrations of human chorionic gonadotrophin and immunoreactive inhibin in early pregnancy and recurrent miscarriage: A longitudinal study

Serum concentrations of immunoreactive inhibin (ir-inhibin) and human chorionic gonadotrophin (HCG) have been measured during the first trimester in a longitudinal study of pregnant women attending a recurrent miscarriage clinic. In 30 singleton pregnancies (Group 1) that continued successfully to term, the median concentration of ir-inhibin initially declined from 1,140 pg/mL at week 4-5 then rose back to comparable values between weeks 7 and 10 but to decline again to reach the significantly lower level of 840 pg/mL (p<0.01) at week 15-16. Serum levels of HCG showed the classical profile of normal pregnancy reaching a median peak value of 65,600 IU/L (1st IRP) at week 8-9. In 7 pregnancies that miscarried but earlier had evidence on ultrasound of an active fetal heart, HCG levels in the first 9 weeks were consistently below the 10th percentile for Group 1 pregnancies (p<0.001). Levels of ir-inhibin were also suppressed but to a lesser extent. In 6 of 7 a fetal pregnancies, HCG levels during the first 9 weeks were again markedly subnormal. The levels of ir-inhibin varied between high normal and subnormal. In none of the pregnancy groups was a correlation found between ir-inhibin and HCG concentrations. In a single pregnancy with an anencephalic fetus, while levels of ir-inhibin and HCG were not depressed, peak values were not reached until week 12. The study shows that the level of ir-inhibin in the maternal serum in early pregnancy is of little value as a prognostic indicator of pregnancy outcome. It confirms that a subnormal HCG level is a useful predictor of early pregnancy failure.