Introduction: Elective oocyte freezing started in Sweden in 2011, a few years after oocyte vitrification was introduced internationally as an effective method for cryopreservation of oocytes. The objective of this study is to describe the age of the women who choose to undergo this procedure, the subsequent utilization of cryopreserved oocytes and the results of autologous in vitro fertilization (IVF).
Material and methods: We conducted a descriptive follow-up study of a subset of women at a private IVF center. All women (n = 254) who electively vitrified oocytes at Nordic IVF Göteborg between 1 August 2011 and 31 August 2017 were included. Ages at oocyte vitrification and warming, number of vitrified oocytes and results of IVF are presented.
Results: A total of 254 women underwent elective oocyte freezing and 38 (15%) of these returned to use their cryopreserved oocytes for autologous IVF before November 2018. In the total cohort, the mean number of vitrified oocytes per woman, undergoing one or more oocyte retrievals, was 7.6 (range 1-37). Their mean age at first vitrification was 36.9 years (range 23-43 years). The mean ages for the subset of women that subsequently used their oocytes for IVF were 38.7 and 42.7 years at vitrification and oocyte warming, respectively. Forty-nine oocyte warming cycles resulting in 42 fresh and 16 frozen embryo transfers, have been performed. Cumulative live birth rate/ongoing pregnancy rates are 63%, 26% and 0% in women of ages 36-37, 38-39 and ≥40 years of age at vitrification, respectively. Five babies have been born and there are 5 ongoing pregnancies.
Conclusions: Elective oocyte freezing has been offered in Sweden for >7 years. The utilization rate has so far been low. Pregnancy results after oocyte warming and IVF are encouraging when oocytes are cryopreserved at an age below 40 years.
Keywords: elective oocyte freezing; in vitro fertilization; oocyte; pregnancy; vitrification.
© 2019 Nordic Federation of Societies of Obstetrics and Gynecology.