Optimal timing of frozen embryo transfer after failed IVF attempt

Abstract

OBJECTIVE: There are currently no data to guide patients regarding the optimal timing of frozen embryo transfer (ET) after a failed fresh IVF-ET cycle. Physicians may intentionally delay starting a frozen ET cycle out of concern that there may be residual effects of ovarian hyperstimulation which may interfere with the natural cycle. The objective of this study is to compare the clinical pregnancy rate (CPR) of frozen ETs in the cycle immediately following a failed fresh ET with frozen ETs which are performed in a later cycle. DESIGN: Retrospective cohort study. MATERIALS AND METHODS: Frozen ET cycles performed from 2003-2007 were included if they were the first frozen ET following an unsuccessful fresh ET. All non-transferred embryos are cultured at the blastocyst stage and frozen if they reach a grade 3BB or better by day 5 or 6. The dates of fresh and frozen ETs were recorded and the number of days between fresh and frozen ET was calculated. To allow for variability in ovulation in the cycle following ovarian stimulation, cycles in which a frozen ET was performed within 50 days of fresh ET were designated as immediate transfers. Cycles were designated as delayed if frozen ET was performed more than 50 days after fresh ET. RESULTS: A total of 271 frozen ETs met criteria, with 105 immediate frozen ETs and 166 delayed attempts (table 1). Cycles with delayed frozen ET had significantly lower CPRs than those with immediate frozen ET, despite no difference in age at time of oocyte retrieval. CONCLUSIONS: CPR was higher with immediate frozen ET compared to delayed frozen ET. The mechanism for the apparent increase in implantation deserves further study. These data should reassure patients who desire to proceed with frozen ET immediately after fresh IVF failure, as there is no medical indication to delay.Table 1Immediate Frozen Transfer (<50d)Delayed Frozen Transfer (>50d)p-valuePatients (n)102166Total # of cycles105166Median time between Fresh and Frozen ET (days)35.0102Average time between Fresh and Frozen ET (days ± std dev)36.2 ± 5.5170.2 ± 193Average age at oocyte retireval (years ± std dev)36.3 ± 4.636.6 ± 5.60.687Average # of embryos transferred ± std dev1.9 ± 0.72.0 ± 0.80.52CPR (%)35.2%21.0%0.01 Open table in a new tab