A 10-year follow-up of reproductive outcomes in women returning after elective oocyte cryopreservation

Abstract Study question What are the reproductive treatment outcomes in women who underwent elective oocyte cryopreservation (EOC) returning to our clinic with a desire for a child? Summary answer Whether to warm oocytes or to first use fresh oocytes for ART depends on age upon returning, but both strategies resulted in favourable reproductive outcomes. What is known already Most affluent countries have observed a trend towards postponement of childbearing, and EOC is increasingly used in an attempt to extend the reproductive lifespan and mitigate age-related fertility decline. Although most follow-up studies after EOC have focused on women who requested oocyte warming, a substantial proportion of women who do not conceive naturally eventually embark for a fertility treatment without using their cryopreserved oocytes. Reports on reproductive outcomes in past EOC users are scarce, and the lack of reproductive treatment algorithms in this group of women hampers efficiency of clinical practice. Study design, size, duration This retrospective observational single-center study includes 843 women who had elective oocyte vitrification for non-medical reasons between 2009 and 2019, and describes the outcomes of the diverse reproductive treatment strategies that were performed in these women when they returned to the same clinic because of a desire for pregnancy until May 2022. Participants/materials, setting, methods Patient characteristics and data of ovarian stimulation of EOC cycles were analyzed, as well as data related to ovarian stimulation and laboratory data of ART in women who pursued fertility treatment with and/or without using their cryopreserved oocytes. The primary outcome was the live birth rate (LBR) per patient after oocyte warming and after ART using fresh oocytes. Secondary outcomes were laboratory outcomes and LBR per embryo transfer. Main results and the role of chance A total of 1353 EOC cycles (1.6 ± 0.9 per patient) were performed. Mean age was 36.5 ± 2.8 years. At the time of EOC 174 (20,6%) women had a partner. On average, 13.7 ± 9.2 mature oocytes were cryopreserved. After 39.9 ± 23.4 months, 231 (27.4%) women returned to the clinic. Upon returning, mean age was 40.4 ± 3.1 years, mean AMH 2.3 ± 2.0 ng/mL, and 150/231 (64,9%) patients had a partner. As a primary approach, 110/231 (47.6 %) past EOC women embarked on oocyte warming, 50/231 (21.6%) had intrauterine insemination, and 71/231 (30.7%) had ART using fresh oocytes. Cumulative LBR (CLBR) was 45.9 % (106/231) and miscarriage rate (MR) was 30.7% (51/166) in the entire cohort. A subset of 90/231 (39.0%) patients exclusively had oocyte warming, at 41.6 ± 3.0 years, with 10.0 ± 5.2 oocytes warmed per patient. 52/231 (22.5%) patients exclusively had ART using fresh oocytes, at a mean age of 39.0 ± 2.8 years, with 9.9 ± 7.4 mature oocytes retrieved per patient. CLBR was 37/90 (41.1%) in the oocyte warming-only group and 25/52 (48.1%) in the OS-only group. MR/transfer was 25.0% and 29.3% in the oocyte warming-only group and the OS-only group, respectively. Limitations, reasons for caution Both the small sample size and the retrospective design are limitations of this study. The decision to embark on a specific reproductive treatment strategy was based on patient preference, after counseling of treatment options. This precludes direct comparison of the efficacy of reproductive treatment options in past EOC users. Wider implications of the findings Reporting of clinical outcomes of women who underwent EOC and returned to the clinic to embark on divergent reproductive treatment strategies is mandatory to establish guidelines for best clinical practice in this growing patient population. Trial registration number Not applicable