Highly specific and sensitive rise in Days 14-17 pro-alphaC inhibin with clinical pregnancy after frozen embryo transfer with ovulatory cycles.

BACKGROUND Pro-alphaC inhibins are luteal derived analytes peaking in the maternal serum as early as Day 16 after conception. We set out to verify a previous post hoc analysis which suggested that pro-alphaC levels measured this early are extremely sensitive in predicting clinical pregnancy success after unstimulated IVF with ovulatory cycles. METHODS Prospective observational study of 246 women undergoing frozen embryo transfer with ovulatory cycles. Serum pro-alphaC and beta-HCG levels at 14-17 days after conception were measured by enzyme-linked immunosorbent assay and grouped according to whether a clinical pregnancy occurred (demonstrable cardiac activity at > or =6 weeks' gestation). RESULTS Of 34 (13.8%) women who achieved a clinical pregnancy, median (25th-75th centile) Days 14-17 pro-alphaC levels were 995 pg/ml (758-1463), 6- to 7-fold higher than levels observed in the remainder who did not fall pregnant (112.8 pg/ml (104-121); P < 0.0001). At a fixed 95% specificity, pro-alphaC was 100% sensitive in predicting clinical pregnancy. The best specificities achieved at 100% sensitivity were; 94.8% for pro-alphaC, 96.7% for beta-HCG and 98.1% when both analytes were combined. CONCLUSIONS Clinical pregnancy is always associated with a release of luteal derived pro-alphaC 14-17 days after conception. Pro-alphaC may play a possible biological role and be a useful clinical biomarker of luteal health.