The association between serum β-hCG on day 24 of pregnancy and ongoing pregnancy in frozen embryo transfer cycles

Objective: To determine the relationship between serum levels of the beta-subunit of human chorionic gonadotropin (beta-hCG) on day 24 of pregnancy during a frozen embryo transfer (FET) cycle and ongoing pregnancy. Methods: In a retrospective cohort study, data were reviewed from women aged 38 years or younger who underwent a FET cycle at Nanfang Hospital, Guangzhou, China, from January 2013 to December 2014. Inclusion criteria were use of hormone-replacement therapy to achieve an endometrial thickness of 8 mm or more, and at least two surviving embryos. Serum beta-hCG on day 24 of pregnancy was assessed in relation to ongoing pregnancy at 12 weeks. Results: Overall, 217 patients who underwent 248 FET cycles were included. The only measure that differed between cycles with (n = 112) and without (n = 136) ongoing pregnancy was beta-hCG level on day 24 of pregnancy (73.0 +/- 65.8 vs 19.4 +/- 34.5 mIU/mL; P < 0.001). Classification tree analysis showed that women with day-24 beta-hCG levels higher than 26.6 mIU/mL had a 75.8% likelihood of ongoing pregnancy. In receiver operating characteristic curve analysis, the corresponding area under curve was 0.845 (95% confidence interval 0.795-0.895). Conclusion: A maternal serum beta-hCG level higher than 26.6 mIU/mL was predictive of ongoing pregnancy at 12 weeks. (C) 2016 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.