Freeze-only versus fresh embryo transfer in a multicenter matched cohort study: contribution of progesterone and maternal age to success rates
In this multi-center matched cohort study, freeze-only cycles were associated with significantly higher pregnancy rates compared with fresh cycles, particularly for patients with progesterone concentration > 1.0 ng/mL at trigger.
Volume 108, Issue 2, Pages 254–261.e4
Ange Wang, M.D., Anthony Santistevan, M.S., Karen Hunter Cohn, Ph.D., Alan Copperman, M.D., John Nulsen, M.D., Brad T. Miller, M.D., Eric Widra, M.D., Lynn M. Westphal, M.D., Piraye Yurttas Beim, Ph.D.
To compare implantation and ongoing pregnancy rates in freeze-only versus fresh transfer cycles.
Retrospective matched cohort study.
Women selected using a matching algorithm for similar distributions of clinical characteristics for a total of 2,910 cycles (1,455 fresh cohort and 1,455 freeze-only cohort).
Main Outcome Measure(s)
Implantation and ongoing pregnancy rates.
Implantation and ongoing pregnancy rates were statistically significantly higher in the freeze-only transfer cohort than in the matched fresh transfer cohort: ongoing pregnancy rate for freeze-only was 52.0% (95% confidence interval [CI], 49.4–54.6) and for fresh was 45.3% (95% CI, 42.7–47.9), odds ratio (OR) 1.31 (95% CI, 1.13–1.51). In a stratified analysis, the odds of ongoing pregnancy after freeze-only transfer were statistically significantly higher for women both above and below age 35 with progesterone concentration >1.0 ng/mL (age ≤35: OR 1.38 [1.11–1.71]; age >35: OR 1.73 [1.34–2.24]). For women with progesterone concentration ≤1.0 ng/mL, no statistically significant difference in freeze-only odds of ongoing pregnancy was observed in either age group. The sensitivity analysis revealed that increasing maternal age alone (regardless of progesterone) trended toward a more beneficial effect of freeze-only cycles. A lower progesterone concentration was associated with statistically significantly higher ongoing pregnancy odds for fresh but not freeze-only cycles.
Freeze-only transfer protocols are associated with statistically significantly higher ongoing implantation and pregnancy rates compared with fresh transfer cycles. This effect is most pronounced for cycles with progesterone >1.0 ng/mL at trigger and may also be stronger for older patients.