Freezing eggs can make in vitro pregnancies less successful

A lot of women in their thirties choose to delay motherhood by freezing their eggs to later fertilize them when they feel the time is right. Cryopreservation of eggs is still a field in its infancy, though, and there’s not much we know about its effects of pregnancy or rate of success. Doctors are steadily gathering stats, though, and a recent analysis suggests there may be some drawbacks to freezing eggs. The report published in the Journal of the American Medical Association suggests fresh eggs have a significantly higher chance of success than cryopreserved ones. This is news for most, even for doctors working in fertility clinics and would be mothers (eventually) should understand this risk when they choose to bank their eggs in a clinic’s frozen basket.

A fragile egg

Human egg storage. Science Photo Library—Getty Images/Science Photo Library RF

Freezing eggs is relatively new. First, drugs are administered which  stimulate the ovaries to produce follicles (which contain the eggs). The developing follicles are monitored and when they are large enough, they are carefully emptied to collect the eggs that they have produced. They are then collected while the patient is under sedation or general anaesthetic, and frozen using liquid nitrogen.

This elaborate multistep-harvesting process can take two to five weeks and cost more than $10,000. Some women, however, think it’s worth it – a high-tech way to beat the biological clock. Ever careful with their human capital, companies like Google and Facebook have offered to fully cover egg cryopreservation for their female employees to keep them on the job for longer.

“The reason I’m so busy is that many women are delaying childbearing,” says  Jamie Grifo, co-director of the Oocyte Cryopreservation Program at New York University’s Fertility Center, showing just how popular freezing egg is becoming. “Most people want their own eggs, not somebody else’s, so egg freezing becomes an insurance policy to be your own egg donor.”

It’s been two years since the American Society of Reproductive Medicine lifted the “experimental” label from egg freezing –– a procedure initially created to help patients undergoing chemotherapy — leading to a surge in demand.

Freezing eggs, however, could lead to poorer results (failed pregnancy) than using fresh eggs. The human egg is an extremely complex, but fragile cell. It’s mostly filled with water and when it’s frozen, the ice crystals can puncture the cell. A recently developed technique called  vitrification uses flash freezing instead of a more slower process and seems to preserve the eggs a lot better. But according to researchers at the Centre for Human Reproduction in New York, the process is still lacking.

The team studied 93 per cent of all donor IVF cycles in the US in 2013 which included data from eight out of 10 fertility clinics. They found women had a 56% chance of becoming mother thorough IVF using fresh eggs, and only became pregnant 47% of the time when using frozen eggs.

The data unfortunately doesn’t factor in important fertility markers like the women’s age or any infertility problems since the records are anonymous. Given the sample size, however, there’s reason to believe these stats reflect an accurate reality.

Becoming pregnant later in life using frozen eggs is still viable, but women undergoing such a procedure should be aware of the risks, especially those past a certain age (45+ most vulnerable) when every egg counts. Women are born with all of the eggs they’ll ever have, and they lose one with each period. More over, the quality of the eggs declines, again, with each period. For example, about half of a 30-year-old woman’s eggs are chromosomally normal but by age 44 this figure drops to 2 percent. Women should freeze their eggs before they reach 38 years of age.

“Egg quality may be negatively affected by cryopreservation and thawing,” said lead author Dr Vitaly Kushnir.

“If egg freezing being done due to impeding exposure to chemotherapy to treat cancer, which can destroy the ovarian reserve and future pregnancy potential, it may be the best available option.

“However, if a woman is considering freezing eggs to postpone fertility for social reasons she may have other, sometimes better, options available based on her age, health, and long term fertility plan.

“Women who are considering electively freezing their own eggs for fertility preservation should be counselled that pregnancy chances with frozen eggs maybe be somewhat lower then with fresh.”