Pregnancy and live-birth rates after transfer of twice-frozen embryos are equivalent to those with once-frozen embryos, researchers from Australia report.
"This preliminary data is reassuring for reproductive endocrinologists that embryos are not significantly harmed by freezing twice," Dr Juliette Koch from IVF Australia and Royal Hospital for Women, Randwick, New South Wales, Australia said.
Dr Koch and colleagues compared the live birth rate of twice-frozen embryo transfers with that of once-frozen embryo transfers generated from the same fresh IVF/intracytoplasmic sperm injection (ICSI) treatment cycle in a small retrospective study of 44 women who had 40 once-frozen and 52 twice-frozen embryo transfer cycles.
Their results appear in the journal Fertility and Sterility.
The survival rates of thawed embryos were lower for twice-frozen embryos than for once-frozen embryos (82% vs. 89%, p=0.012).
The pregnancy rates and live birth rates, however, didn't differ significantly between the once-frozen (11 pregnancies and 6 live-births from 43 blastocyst transfers) and twice-frozen (13 pregnancies and 7 live births from 52 blastocyst transfers) embryos.
Miscarriage rates didn't differ between transfers of once-frozen (5 miscarriages) and twice-frozen (6 miscarriages) embryos either, and there were no birth abnormalities detected in either group.
"It is important to continue to assess outcomes, including long-term outcomes of development," Dr Koch concluded. (Reuters Health/ May 2011)
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