Efficacy of oocyte vitrification combined with blastocyst stage transfer in an egg donation program.
Level 3 - non-randomized controlled study
Non-randomized comparative cohort study comparing vitrified versus fresh donor oocytes.
PubMed 21303777 · doi:10.1093/humrep/der008
What was done
A comparative cohort study evaluated outcomes of oocyte vitrification combined with blastocyst transfer in an egg donation program. From 78 donors, 1098 oocytes were collected, with 312 allocated to the vitrification group (34 recipients) and 786 to the fresh control group (58 recipients). Outcomes measured included oocyte survival, fertilization rate, Day 2 cleavage rate, blastocyst formation rate, embryo quality, pregnancy rate, implantation rate, and miscarriage rate.
What was found
Vitrified oocytes had an 89.4% post-thaw survival rate. Comparing the vitrified group to the fresh group, fertilization rates were 76.1% versus 87.5%, Day 2 cleavage rates were 96.3% versus 98.0%, and blastocyst formation rates were 41.3% versus 45.3% (all reported as having no difference). Clinical outcomes were also similar between vitrified and fresh groups: pregnancy rates were 61.8% versus 60.0%, implantation rates were 43.9% versus 42.9%, and miscarriage rates were 9.5% versus 5.9%.
Why it matters
The findings demonstrate that vitrified donor oocytes retain developmental competence to reach the blastocyst stage and achieve pregnancy and implantation rates comparable to fresh oocytes. This supports the utility of oocyte vitrification in donor egg programs and broader fertility preservation protocols.
Limits
The study was non-randomized, presenting potential selection and allocation bias between recipient groups. The sample size was relatively small (34 vitrified versus 58 fresh recipients), live birth rates and neonatal outcomes were not reported in the abstract, and statistical test values such as p-values or confidence intervals were not provided.
Cited by
- supports In standard IVF culture, approximately 90% of frozen eggs survive thawing, 75% fertilize, 50% reach the blastocyst stage, and a genetically normal (euploid) embryo has roughly a 65% chance of resulting in a live birth.