Embryo freezing by vitrification improves frozen embryo cycle results

This is one of a series of news items from abstracts of studies presented at the Annual Meeting of the American Society for Reproductive Medicine as complied by Dr. David Meldrum, Scientific Director of Reproductive Partners. We appreciate the enormous amount of work it takes to compile and comment on these abstracts.

 whanEmbryo freezing by the newer method of vitrification is showing promise in improving the chance of success in frozen embryo cycles, according to two poster presentations.

In one, conventional freezing of poor quality day 3 embryos was compared to vitrification/warming. Embryo survival was higher, cell (blastomere) loss was lower, and pregnancy rate was 0% for conventional vs 6/11 (55%) in which vitrification was used. Of the 6 pregnancies, two aborted.  The authors suggested that vitrification allows consideration of cryopreserving poorer quality embryos. Further experience will be necessary to evaluate the miscarriage rate, because chromosome abnormalities (aneuploidy) is more common in lower quality day 3 embryos.

In another presentation, the implantation rate with cryoloop vitrification of day 3 embryos was the same as for blastocysts (over 200 cycles in each group, 26% and 25% respectively). This shows that vitrification of day 3 embryos is highly efficient considering that only 50% progress to blast. This finding might suggest beneficial in vivo co-culture and embryo-endometrial cross-talk effects that occur to a lesser degree with blast transfer. Alternatively, the lack of difference could have been due to low power.

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