Clinical outcomes of a vitrified donor oocyte programme: A single UK centre experience

To assess the survival rate of vitrified oocytes used in an egg recipient programme and compare the clinical outcomes of pregnancy and live-birth rates per warmed oocyte with fresh autologous oocytes. The differences in the obstetrical outcomes between the two groups were also studied.

A prospective case control study from a single in-vitro fertilisaton (IVF) Centre in UK SETTING: Centre of Reproductive and Genetic Health (CRGH), London POPULATION: Vitrified oocytes from egg donors and autologous fresh oocytes from patients attending for an IVF cycle METHODS: The study group consisted of 1490 vitrified oocytes, which were obtained from 145 egg donors who underwent a stimulation cycle at CRGH Centre. The control group included 145 age-matched women who underwent intra cytoplasmic sperm injection (ICSI) treatment with their own oocytes (n = 1528). The clinical outcomes clinical pregnancy rates (CPR) and live-birth rates (LBR) and obstetrical outcomes (gestational age and weight at delivery) were compared between the two groups. Statistical analysis of the summary data and logistic regression analysis was performed using statistical packages (SPSS Version 23 and Stata 2015). The percentages of all parameters in the cases and control groups were compared by Fisher's exact test. A statistical significance level of 5% was adopted throughout the study.

Survival rate per thawed oocyte, clinical pregnancy rate and live-birth rate per embryo transfer was compared to the autologous oocyte group RESULTS: The survival rate of vitrified oocytes was 73.6% (95% CI: 71.3-75.8%). The clinical pregnancy rate (per embryo transfer) using vitrified oocytes was found to be 51.8% compared to 59.3% in the control group. The live birth rate per embryo transfer in the vitrified oocyte group was 46% (95% CI 37.4-54.7%) compared to 57.1% (95% CI 48.5-68.5%) in the control group. The live-birth rate per thawed oocyte was found to be 4.2%. The gestational ages of the fetus at delivery in both the groups were comparable 39.0 (95% CI 32.7-41.9%) and 39.1 (95% CI 25.6-42.0) (p = 0.38). There was no statistically significant difference in the birth weight between the study and the control group 3100 g (750-4337) and 3232 g (1616-4500) respectively (p = 0.28).

This is the first study reporting on the efficacy of a vitrified donor oocyte programme from within the UK. There were no significant differences in the obstetrical outcomes between vitrified donor oocytes and autologous oocytes. The above data will be encouraging for women who are undertaking egg freezing for medical and or social reasons.