Fertilization and embryo development in fresh vs. vitrified oocytes with sperm from men with nonobstructive azoospermia.

OBJECTIVE

To examine early embryo development of fresh vs. vitrified oocytes fertilized with microdissection testicular sperm extraction (mTESE) sperm from men with nonobstructive azoospermia.

DESIGN

Retrospective cohort SUBJECTS: Couples undergoing treatment for severe male factor infertility at a university-affiliated academic medical center EXPOSURE: Intracytoplasmic sperm injection (ICSI) of either fresh or vitrified oocytes with fresh mTESE sperm retrieved from men with nonobstructive azoospermia between January 2013 and December 2023.

MAIN OUTCOME MEASURES: Proportion of good quality day 3 embryos, defined as six or more cells, per oocyte inseminated. Normal 2 pronuclei (2pn) fertilization rate per oocyte inseminated and the proportion of good quality day 3 embryos per normally fertilized oocyte. Analyses evaluating fresh vs. vitrified oocytes were conducted in self-matched individuals, across the whole population cohort, and using a 1:2 age-matched comparison.

RESULTS

No significant difference in median number of 2pn fertilizations (3 in fresh vs. 2 in vitrified) or 2pn fertilization rate per inseminated oocyte (48% in fresh vs. 33% in vitrified) was observed in self-matched comparisons. Similarly, the proportion of good quality day 3 embryos per oocyte inseminated (median 25% fresh vs. 21% vitrified) and proportion of good quality day 3 embryos per normally fertilized embryo (median 61% fresh vs. 50% vitrified,) were similar between groups. Similar results were seen in the whole population and 1:2 age-matched comparisons.

CONCLUSION

The use of fresh mTESE sperm for ICSI with either fresh or vitrified oocytes yielded equivalent fertilization and day 3 embryo development rates, assessed on a self-matched, whole population, or 1:2 age-matched comparison between vitrified and fresh oocytes. Low fertilization rates observed with ICSI in this population underscores the importance of obtaining an adequate number of oocytes, whether fresh or vitrified, to optimize pregnancy rates.