Well-Being Medical Advances

Success of egg freezing depends on these two factors, new study finds

Patients who froze their eggs before they turned 38 or froze more eggs had about a 50 percent birth rate.
woman with hands in front of body, outline of uterus
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Story at a glance


  • Egg freezing involves a process of inducing egg production and retrieving them for freezing and storage for future fertilization.

  • Not all eggs can make good embryos.

  • A study from an NYU fertility center finds that overall birth rates among their patients is 39 percent.

Most women who tried to become pregnant through the process of egg freezing did not end up having a baby, according to a study of more than 500 such women over a 15-year span.  

The fertility team at New York University Langone Center found that around 1 in 3 patients who chose to freeze their eggs had a baby after in vitro fertilization, and the success rate depended largely on factors: age and the number of eggs frozen.  

Egg freezing — a method where a patient’s eggs are extracted, frozen and stored — has become an increasingly popular decision among women, especially during the COVID-19 pandemic. To freeze their eggs, patients take synthetic hormones to stimulate egg growth in their ovaries and undergo an egg retrieval process under anesthesia.

Results from NYU’s study suggest that the process is not a guarantee for a future baby. Overall, the final live birth rate for all 543 patients was 39 percent. For patients who froze their eggs before they were 38 years old or who thawed 20 or more eggs, this birth rate was about 50 percent. 

“Egg freezing is invasive and it comes with serious short- and long-term physical and mental health risks,” writes Pamela Mahoney Tsigdinos in an Opinion for WIRED. “To secure any eggs you must first submit to a demanding series of rigorously scheduled blood tests, hormone injections, and ultrasounds conducted over several weeks prior to the actual egg retrievals. 

The process itself is not always covered by insurance, and if it is, may only be partially covered. Out-of-pocket, it can cost tens of thousands of dollars and that doesn’t include annual storage costs. 

NYU’s researchers found that the number of eggs frozen and how old the patient was at the time of egg retrieval were the biggest factors in determining the “final live birth rate,” or the success rate of thawing eggs, creating viable embryos, implantation and pregnancy all the way through to live birth. 

The patients who retrieved their eggs for cryopreservation, or freezing, before they turned 38 years old had a better chance for success. Patients who froze more eggs had a better chance of some of those eggs becoming viable embryos. 

“The reality is most eggs don’t make good embryos,” James Grifo, who is director of the fertility center at New York University Langone Center, told The New York Times. “The more eggs you have, the better the chance.” 

The average age when individuals froze their eggs was 38.3 years old. The average length of time between cryopreservation and thawing was 4.2 years. Eggs survived freezing and thawing at a rate of 79 percent. 

They published their findings in the journal Fertility and Sterility in July. Although the NYU team was able to use data from a good number of patients over 15 years, they do caution that larger studies are needed.