More than 40% of women who chose to freeze their eggs in their 30s were able to have babies later in life when they returned to the fertility clinic, according to research presented today (Monday) at the 39^th annual meeting of the European Society of Human Reproduction and Embryology (ESHRE).

However, many of the women in the study who had frozen their eggs (known as elective oocyte cryopreservation) had not returned to the fertility clinic and many who did return chose fertility treatments that did not involve their frozen eggs.

The research was presented by Dr Ezgi Darici, a clinical fellow at the Centre for Reproductive Medicine at Universitair Ziekenhuis Brussel (Belgium).

Increasing numbers of women are choosing to freeze their eggs in the hope that it will enable them to have children later in life. However, there is a lack of evidence on how effective this strategy is. To our knowledge, this is one of the first and largest reports of reproductive outcomes in women who had elective oocyte cryopreservation at a European fertility center.”

Dr Ezgi Darici, Clinical Fellow, Centre for Reproductive Medicine, Universitair Ziekenhuis Brussel (Belgium)

The study included 843 women who had elective oocyte cryopreservation for non-medical reasons at the Centre for Reproductive Medicine between 2009 and 2019. Their average (mean) age at the time was 36 and the majority did not have partners. By May 2022, 231 (27%) of the women had returned to the centre for treatment. Their average (mean) age when they returned was 40 and the majority did have partners.

A total of 110 out of the 231 women who returned (48%) used their frozen eggs as part of their fertility treatment. Fifty of the women (22%) had intrauterine insemination (where sperm are delivered directly into the womb) and 71 out of 231 (31%) had fertility treatments such as IVF using fresh eggs. The average age of the women using frozen eggs was 42 while the average age of women using fresh eggs was 39.

The overall proportion of women who gave birth to a live baby out of all 231 women (known as the cumulative live birth rate because it includes all live births following any of the fertility treatments) was 46% (106 out of 231 women). The miscarriage rate was 31%.

Among the women who had treatment involving their frozen eggs, 41% had babies. Among those who had treatment involving fresh eggs, 48% had babies. The miscarriage rates were 25% in those who used frozen eggs and 29% in those using fresh eggs.

Dr Darici said: “We found that many women who chose to freeze eggs in their 30s had not yet returned for fertility treatment. Among those who did return for treatment, around half used their frozen eggs. These were older women on average. The choice of whether to use fresh or frozen eggs is made based on what treatment is best for each individual woman and factors such as the woman’s age are important. We cannot really compare the two groups as there will be many differences that could underlie any disparity in pregnancy and birth rates. However, women who had frozen their eggs had several options open to them and we found positive rates of pregnancy and birth regardless of whether the women had fertility treatment with fresh or frozen eggs.”

The researchers acknowledge that the study includes a relatively small number of people, and it is retrospective, meaning it looks back on what has happened in the past.

The chair of ESHRE, Professor Carlos Calhaz-Jorge from the Northern Lisbon Hospital Centre and the Hospital de Santa Maria in Lisbon (Portugal), was not involved in this research. He said: “The aim of elective oocyte cryopreservation is to mitigate the risk of infertility in later life. However, this can be an expensive choice and there is a lack of evidence to show how useful it is. This study suggests that frozen eggs can be useful for older women who are struggling to have children; however, we need much more research to prove that this is the case. Routine reporting on fertility outcomes for women who opt to freeze their eggs would help build up a clearer picture. This could help establish guidelines for young women who are considering freezing their eggs.”