"Try until the last?"-the relevance of fresh embryo transfer outcomes for subsequent same-cohort vitrified-warmed cycles

Purpose: Taking into consideration earlier attempts at assisted reproduction and previous pregnancies allows a more differentiated approach when counseling couples regarding their chances in assisted reproductive treatments. The aim of this study was to investigate whether the outcome of fresh embryo transfers affects subsequent same-cohort vitrified-warmed cycles.

Methods: This retrospective cohort study analyzes the outcome of all fresh and frozen embryo transfers (n = 8118) between January 1, 2011, and December 31, 2022. All women who received fresh or frozen embryo transfers at Kepler University Hospital Linz were included. The use of donor eggs, previously cryopreserved oocytes, and freeze-all cycles were excluded from the analysis.

Results: Positive serum βhCG after a fresh cycle has a significant impact on the chances of positive βhCG in a subsequent vitrified-warmed cycle (36.3% [33.2%, 39.5%]; P = 0.002). Negative βhCG after a fresh cycle does not predict the outcome of the following same-cohort embryo transfer (33.1% [30.7%, 35.7%], P = 0.726). Pregnancy rates of the first, second, third, and fourth same-cohort vitrified-warmed embryo transfer remain continuously high, with 32.8%, 30.8%, 28.9%, and 27.1%, respectively.

Conclusions: Positive serum βhCG after a fresh embryo transfer has a positive predictive value for the outcome of a subsequent vitrified-warmed embryo transfer. Couples with a negative fresh cycle should not be discouraged from continuing fertility treatment using same-cohort frozen embryos.

Trial registration: This study was prospectively registered at the German Clinical Trials Register on September 5, 2023 (DRKS00032552).