Store eggs in a biobank
Cryopreservation of eggs increases the success of IVF at a later age
Elena Kleshchenko, PCR.news
In the USA, the proportion of women giving birth at 20 has decreased, and the proportion of women giving birth at 30-40 has increased. The average age of birth of the first child has increased from 19 years in 1984 to 30 years in 2021, in many megacities it is even higher. At the same time, less than 30% of women aged 40 who are trying to conceive a child using in vitro fertilization (IVF) become pregnant, and about 20% give birth to live children as a result. These data were collected until 2013 by the Centers for Disease Control and Prevention of the United States in almost 500 infertility treatment clinics (calculated for one IVF cycle). It also follows from them that the use of frozen eggs taken from a woman at a young age, and not right before IVF, improves results.
A team from the Grossman School of Medicine and the Langone Health Fertility Center at New York University has found out how egg freezing affects the success of IVF. Specialists of the Fertility Center of New York University are pioneers in the development of cryopreservation technology: their first child from a thawed egg was born in July 2005. It is necessary to accurately assess the effectiveness of the technology so that women do not have false expectations, the authors note.
The study was based on the results of egg thawing in real clinical experience for 15 years, from 2005 to 2020. The authors collected data on 543 patients, their average age at the time of the first egg freezing was 38 years with a spread of 27-44 years, most were 35-40 years old. (The optimal age for egg freezing is 35 years or less). In total, 800 cycles of egg cryopreservation, 605 defrosting and 436 embryo transfers were considered. For cryopreservation, both slow cooling (an older method) and vitrification in liquid nitrogen were used.
Fertilization of all eggs was carried out using intracytoplasmic sperm injection. Embryos were cultured for 3-7 days, for preimplantation genetic testing (PGT), a biopsy of the trophectoderm (the surface layer of the blastocyst) was taken; sometimes cryopreservation of the embryo was performed at the blastocyst stage (5-7 days). PGT was performed using microchip hybridization or NGS. The final results included only women who gave birth or used all cryopreserved oocytes and embryos.
In general, 39% of women gave birth to at least one child from thawed eggs, which is comparable to the results of IVF without freezing (taking into account multiple attempts). However, in all age groups — including the oldest participants — women who thawed more than 20 mature eggs, the proportion of live births reached 58%, which can be considered a brilliant success. The authors clarify that before 2012, egg freezing was not covered by insurance, and many patients who went for it "were concerned about their current, not future reproductive potential," that is, they had certain problems with reproductive health. Among women under the age of 38 who have thawed more than 20 eggs, 70% have given birth to at least one child, many — more than one. A total of 211 children were born. The duration of storage of frozen eggs did not play a role.
The authors add that preimplantation genetic testing of embryos and eggs has reduced the frequency of miscarriages and increased the number of live births per transfer, however, they emphasize that there have not yet been any special studies evaluating the effect of PGT on the effectiveness of embryo transfers from frozen eggs. PGT also allows for the transfer of a single embryo, and a singleton pregnancy is safer for both mother and child. Among the disadvantages of PGT, they note financial costs, a low but non-zero level of errors and possible moral damage from undesirable results.
Article by Cascante et al. Fifteen years of autologous oocyte thaw outcomes from a large university-based fertility center is published in the journal Fertility and Sterility.
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