Twice-frozen embryos are no detriment to pregnancy success: a retrospective comparative study

ObjectiveTo compare the pregnancy rates (PR) and live birth rates in once- versus twice-frozen ET treatment cycles in the same cohort of women.DesignA retrospective study.SettingFertility clinics, IVF Australia, New South Wales.Patient(s)The study population was all women who underwent thawing of twice-frozen embryos between January 2003 and May 2009.Intervention(s)Twice-frozen, twice-thawed embryos.Main Outcome Measure(s)Pregnancy and live birth rate.Result(s)There were 44 women who had 52 twice-frozen ET treatment cycles. The mean age of the women was 32 ± 4.4 years and the mean number of embryos transferred was 1.1 in both the once-frozen and twice-frozen ET treatment cycles. Twice-frozen embryos had a lower post-thaw survival rate compared with the once-frozen embryos. There was no significant difference in the clinical PR or live birth rate per ET between twice-frozen and once-frozen ETs.Conclusion(s)Twice-frozen-thawed embryos have a lower post- thaw survival rate but equivalent pregnancy and live birth rates to once-frozen embryos. Further studies are necessary to confirm our findings and to assess long-term safety outcomes.