Egg freezing, IVF and age-related fertility decline
A US study of elective fertility preservation has found that 70% of women who froze eggs when they were younger than 38 — and thawed at least 20 eggs at a later date — had a baby.
The report is based on 15 years of 'real life' frozen egg thaw outcomes for women who had delayed childbearing and faced natural, age-related fertility decline. It also found that a considerable number of the women studied had more than one child through egg preservation. Reportedly, there were a total of 211 babies from egg freezing.
In comparison — and using fresh eggs or embryos from women trying to conceive — at age 40 fewer than 30% undergoing in vitro fertilisation (IVF) become pregnant and fewer than 20% gave birth to live babies as a result, according to statistics gathered by the Centers for Disease and Prevention from the nation's nearly 500 fertility clinics.
Egg freezing and thawing at a later date provides a higher pregnancy success rate than using fresh embryos during assisted reproductive technology, said authors of the study led by experts at NYU Grossman School of Medicine and the NYU Langone Fertility Center.
"Our findings shed light on the factors that track with successful births from egg freezing, which include careful screening of embryos to be thawed and implanted," said study lead author Sarah Druckenmiller Cascante, MD, fellow in the Division of Reproductive Endocrinology and Infertility, within the Department of Obstetrics and Gynecology at NYU Langone.
"A better understanding of the live birth rate from egg freezing for age-related fertility decline is necessary to inform patient decision-making.
"Importantly, our study is based on actual clinical experience rather than mathematical modelling with limited data, which is most of what has been published on the chance of births from egg freezing thus far," Cascante said.
Within the study, 543 patients participated with an average age of 38 years old at the time of the first egg freeze, which is older than the optimal age to freeze eggs (35 years old or younger). These patients underwent 800 egg freezing cycles, 605 egg thaws and 436 embryo transfers between 2005 and 2020.
The investigation found that overall, 39% of women between 27 and 44 years old, with a majority between 35 and 40 years old at egg freeze, had a least one child from their frozen eggs, which is comparable with age-matched IVF outcomes.
Across all ages, women who thawed more than 20 mature eggs had a 58% live birth rate, which was profound and unexpected as this group included patients past their reproductive prime. In fact, 14 patients who froze eggs at the age of 41–43 years successfully had children from their frozen eggs. As noted, women under 38 years old who had 20 or more mature eggs thawed achieved a 70% live birth rate per patient. The length of frozen egg storage did not change the success rate, the study found.
Results also showed that preimplantation genetic screening with embryos from frozen and eventually thawed eggs resulted in lower miscarriage rates and higher live birth rates per transfer. Such screening also allows for single embryo transfers, yielding singleton pregnancies, which are safer for both the mother and child, according to the authors.
"Freezing eggs at a young age becomes an option to be one's own egg donor at advanced age. As younger patients freeze eggs and do more than one cycle, the success rates will be even higher than reported in this study," said study senior author James A Grifo, MD, PhD, director of the Division of Reproductive Endocrinology and Infertility and the NYU Langone Fertility Center.
Grifo, also a professor in the Department of Obstetrics and Gynecology at NYU Langone, cautioned that the study was limited by the number of patients. Future larger studies are underway to increase the data set from which patients can benefit and model their expected success rates. He said that additional studies from a variety of geographic locations and centre types are also necessary.
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