Outcomes of female fertility preservation with cryopreservation of oocytes or embryos in the Netherlands: a population-based study.

Study question: What are the reproductive outcomes of patients who cryopreserved oocytes or embryos in the context of fertility preservation in the Netherlands?

Summary answer: This study shows that after a 10-year follow-up period, the utilization rate to attempt pregnancy using cryopreserved oocytes or embryos was 25.5% and the cumulative live birth rate after embryo transfer was 34.6% per patient.

What is known already: Fertility preservation by freezing oocytes or embryos is an established treatment for women with a risk of premature ovarian failure (caused by a benign or oncological disease) or physiological age-related fertility decline. Little is known about the success of cryopreservation, the utilization rate of oocytes or embryos, or the live birth rates.

Study design, size, duration: A retrospective observational study was performed in the Netherlands. Data were collected between 2017 and 2019 from 1112 women who cryopreserved oocytes or embryos more than 2 years ago in the context of fertility preservation in 10 IVF centers in the Netherlands.

Participants/materials, setting, methods: A total of 1112 women were included in this study. Medical files and patient databases were used to extract data. Women were categorized based on indication of fertility preservation: oncological, benign, or non-medical. To indicate statistical differences the t-test or Mann-Whitney U test was used. Kaplan-Meier analyses were used for time endpoints, and log-rank analyses were used to assess statistical differences. The study protocol was approved by the medical ethics committee.

Main results and the role of chance: Fertility preservation cycles have been performed increasingly over the years in the Netherlands. In the first years, less than 10 cycles per year were performed, increasing to more than 300 cycles per year 10 years later. Initially, embryos were frozen in the context of fertility preservation. In later years, cryopreservation of oocytes became the standard approach. Cryopreservation of oocytes versus embryos resulted in comparable numbers of used embryos (median of 2) for transfer and comparable live birth rates (33.9% and 34.6%, respectively). The 5-year utilization rate was 12.3% and the 10-year utilization rate was 25.5%. The cumulative clinical pregnancy rate was 35.6% and the cumulative live birth rate was 34.6% per patient. Those who had fertility preservation due to benign diseases returned earlier to use their cryopreserved embryos or oocytes.

Limitations, reasons for caution: The follow-up period after the fertility preservation procedure varied between patients in this study and not all frozen oocytes or embryos had been used at the end of this study. This might have led to underestimated outcomes reported in this study. Furthermore, intention to treat cannot be fully determined since women who started the fertility preservation procedure without success (cancellation due to low response) were not included in this study.

Wider implications of the findings: This study provides data on the reproductive outcomes after various indications of fertility preservation. This knowledge can be informative for professionals and future patients to improve counseling and informed decision making regarding ovarian stimulation in the context of fertility preservation.

Study funding/competing interest(s): No funding was obtained for this study. The authors have no conflicts of interest to declare related to this study. V.T.H. received grants paid to the institute for studies outside the present work from AstraZeneca, Gilead, Novartis, Eli Lily, Pfizer, and Daiichi Sankyo. V.T.H. received consulting fees from Eli Lily outside the present work. M.G. received grants paid to the institute for studies outside the present work from Guerbet and Ferring. E.M.E.B. received a grant from The Dutch Network of Fertility Preservation for a study outside the present work.

Trial registration number: N/A.