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Frozen-thawed transfer cycles: are they comparable with fresh?
E V Mocanu1, E Cottell, K Waite
1Human Assisted Reproduction Ireland, Rotunda Hospital, Dublin. emocanu@rcsi.ie
Irish Medical Journal
|August 15, 2008
Summary
Frozen-thawed zygote transfer success rates are lower than fresh cycles, with higher pregnancy loss. However, cryopreservation of good quality zygotes still offers optimal outcomes for subsequent frozen embryo transfer treatments.
Area of Science:
- Reproductive Medicine
- Embryology
- Assisted Reproductive Technology (ART)
Background:
- Cryopreservation of zygotes is an established procedure in assisted reproductive technology (ART).
- The efficacy of using frozen-thawed (day 2) zygotes compared to fresh cycles requires thorough evaluation.
Purpose of the Study:
- To compare the success rates of frozen-thawed zygote transfer with fresh ART cycles.
- To analyze clinical pregnancy rates, implantation rates, and pregnancy loss in both frozen and fresh treatment groups.
Main Methods:
- Prospective follow-up and analysis of all frozen-thawed (FZT) and fresh ART cycles over a 12-month period.
- Data collection included patient numbers, thaw-survival rates, clinical pregnancy rates, implantation rates, and pregnancy loss rates.
Main Results:
- The overall thaw-survival rate for zygotes was 71.7%.
- Clinical pregnancy rates per transfer were 21% for FZT cycles versus 29.1% for fresh cycles.
- Implantation rates were 12.3% for FZT and 16% for fresh cycles, with a higher pregnancy loss rate (29% vs. 18.3%) in the FZT group.
Conclusions:
- While fresh cycles show higher success rates, cryopreservation of good quality zygotes provides optimal outcomes for subsequent frozen treatments.
- The findings support the consideration of elective single zygote transfers in ART.
