Predicting in vitro fertilization success: establishing human chorionic gonadotropin cutoffs after frozen embryo transfers for untested and preimplantation genetic tested embryos.

PURPOSE: The early post-embryo transfer period lacks well-defined beta-human chorionic gonadotropin (hCG) thresholds to distinguish viable from non-viable pregnancies after frozen embryo transfer (FET). This study aimed to identify a day-14 post-FET hCG cutoff that predicts fetal heart tones (FHT) and live birth (LB), and to assess its utility in guiding decisions regarding continuation of progesterone support.

METHODS

A retrospective cohort study was conducted at a single academic center including 1681 single-embryo FETs from 2021 to 2023. Demographic, cycle, and embryologic variables were extracted from medical records. Serum hCG levels were measured 14 days post-FET. Receiver operating characteristic analyses identified optimal hCG thresholds for predicting FHT and LB. Outcomes were compared using appropriate parametric and nonparametric statistical tests.

RESULTS

Overall, 59.0% of transfers resulted in FHT and 56.0% in LB. A hCG cutoff of 391.7 mIU/mL predicted LB with 96.3% sensitivity and 82.7% specificity (AUC = 0.936). Patients with hCG ≥ 391.7 mIU/mL had markedly higher FHT (92.1%) and LB (87.6%) rates than those below this threshold (6.0% and 5.4%, respectively). The lowest hCG associated with LB was 119.9 mIU/mL. Findings were consistent in the PGT-A subgroup.

CONCLUSION

A day-14 hCG value of ≥ 391.7 mIU/mL strongly predicts FHT and LB after FET and may serve as a clinically meaningful threshold for early counseling and decisions regarding progesterone continuation. However, rare live births occur at lower levels, underscoring the need for individualized interpretation and clinical context.