Early β-hCG levels predict live birth after single embryo transfer.

Purpose: Specific serum beta human chorionic gonadotropin (β-hCG) parameters that can predict live birth after an embryo transfer have yet to be defined.

Methods: We performed a retrospective cohort study of 1,028 patients with a detectable β-hCG who underwent a single embryo transfer between 2002 and 2019 at a large academic center. Two β-hCG parameters were examined in relation to live birth: 1) "doubling" defined as β-hCG doubling over 48 h and 2) "reaching 100" defined as a β-hCG ≥ 100 mIU/mL by 15 days after oocyte retrieval (AOR).

Results: One thousand three hundred forty cycles involving a single embryo were analyzed. Two thirds were frozen embryos and 86% were blastocyst transfers. Preimplantation genetic testing was performed in almost 30% of cycles. When β-hCG levels "doubled," a live birth occurred in 80.7% of cycles and when β-hCG levels "reached 100" by 15 days AOR, live birth occurred in 81.6% of cycles. When β-hCG levels both doubled and reached 100 by 15 days, AOR 85.4% cycles resulted in live birth. A multiple logistic regression model to control for patient and cycle level factors revealed a live birth odds ratio (OR) of 8.0 (95% CI 5.7-11.1) when β-hCG "doubled" and an OR of 21.2 (95% CI 14.3-31.5) when β-hCG "reached 100." When both these latter parameters were met, the OR was 12.5 (95% CI 8.9-17.8).

Conclusion: β-hCG parameters of "doubling" and "reaching 100" by 15 days AOR are robust predictors of live birth and can aid in patient counseling regarding pregnancy outcomes soon after single embryo transfer.