Decreased pregnancy and live birth rates after vitrification of in vitro matured oocytes.

PURPOSE: To assess effects on fertilization rate, embryo quality, pregnancy, and live birth rates of vitrification and warming of oocytes that matured in vitro (vIVM) compared to fresh in vitro maturation (fIVM) cycles.

METHODS: A retrospective cohort study conducted at a university hospital-affiliated IVF unit. Fifty-six cycles of vIVM cycles and 263 fIVM in women diagnosed with polycystic ovarian syndrome (PCOS) ovaries were included in the analysis. The study group included PCOS patients who failed ovulation induction with intrauterine insemination and were offered IVM cycle followed by oocyte vitrification and warming. The embryological aspects and clinical outcomes were compared to those of controls undergoing fresh IVM cycles during the same period. The main outcome measure was live birth rate.

RESULTS: One thousand seventy oocytes were collected from 56 patients and underwent vitrification and warming. In the control group, 4781 oocytes were collected from 219 patients who had undergone a fresh IVM cycle. Oocyte maturation rates were similar between the groups (mean ± SD: 0.7 ± 0.2 vs. 0.6 ± 0.2, for vIVM and fIVM, respectively). Survival rate after warming was 59.8%. Fertilization and embryo cleavage rates per oocyte were significantly lower in the vIVM group. Clinical pregnancy (10.7 vs. 36.1%) and live birth rates (8.9 vs. 25.9%) per cycle were significantly lower in the vIVM group than those in the fIVM group (P = 0.005 and P < 0.001, respectively). Five healthy babies were born in the vIVM group.

CONCLUSIONS: The reproductive potential of vitrified IVM oocytes is impaired. This injury likely occurs through vitrification and warming.