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 β-hCG on day 24 of pregnancy was assessed in relation to ongoing pregnancy at 12 weeks.
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 β-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 β-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).
A maternal serum β-hCG level higher than 26.6 mIU/mL was predictive of ongoing pregnancy at 12 weeks.