Increased Day 15–17 Serum Pro-αC Inhibin Levels Specific to Successful Pregnancy

Abstract

In early pregnancy, serum levels of the luteal-derived hormone pro-␣C inhibin peak by the second week after conception. Whether this early rise is biologically important and a consistent feature of only successful pregnancy is unknown. We undertook a prospective cross-sectional study to determine whether serum pro-␣C inhibin levels at d 15-17 are predictive of a successful clinical in vitro fertilization pregnancy and compared levels between fresh embryo transfer (ET) and frozen-thawed ET. Median (95% confidence interval) pro-␣C inhibin levels were 68 (57-76) pg/ml in 204 women who did not become clinically pregnant after ET, significantly lower than in either 90 women who became clinically pregnant after fresh ET and who had 3139 (1684 -4220) pg/ml or in 39 women with a successful frozen ET who had 877 (678 -1111) pg/ml. Pro-␣C was highly sensitive and specific in predicting clinical pregnancy success but did not improve on the performance of human chorionic gonadotropin. Pro-␣C inhibin levels were not correlated with progesterone or human chorionic gonadotropin. Levels were no higher in singleton compared with multiple pregnancies and did not increase across gestation, suggestive of a luteal source. The increase in circulating pro-␣C inhibin in very early pregnancy is highly specific to clinical pregnancy, suggesting a possible biological role in early gestation. (J Clin Endocrinol Metab 89: 4464 -4468, 2004)