More women than ever are freezing eggs, but many are leaving the decision too late

Between 2010 and 2018, the number of oocyte vitrification cycles in Australia and New Zealand skyrocketed by 860%. In Victoria, a report showed a 30% increase in women storing eggs in 2019-20 compared to the year before.

The upward trend is continuing, with more women than ever freezing their eggs to preserve fertility.

But just how successful is egg freezing?

“The answer is that it really depends on the woman’s age when she comes to freeze her eggs,” fertility specialist and consultant gynaecologist Dr Kate McIlwaine said in a Healthed podcast.

Technological advances have dramatically improved freeze-thaw rates in the last 15 years so that about 99% of thawed eggs are viable—but technology can’t counteract the biology of ovarian ageing.

If a woman is under 35 years of age, and she freezes 20 eggs, she’s got a 90% probability of at least one live birth from those eggs. If she freezes the same number of eggs at age 36, that probability drops to about 84%, and if she freezes the eggs at age 40, the probability of a live birth would be just over 50%, Dr McIlwaine said.

Ideally, outcomes are best when women freeze their eggs before the age of 30, but success rates reduce significantly after age 35.

Lifestyle can’t prevent ovarian ageing

Unfortunately, staying healthy and fit isn’t enough to defy the odds.

“I think age trumps everything when it comes to egg quality and quantity,” Dr McIlwaine said. “We are born with 1 to 2 million eggs and by the time we’re a teenager, we’ve got about 400,000 eggs left. By the time we’re 40 we’ve only got 10% of our original supply and eggs accumulate DNA damage and changes in the mitochondria,” Dr McIlwaine said.

“So even if a woman is fit and healthy and goes to the gym and maintains a healthy weight and doesn’t smoke, they’re all great things and they may help with the egg quality, but unfortunately from the age of 35 all women are on a rapid decline with regards to egg quality and quantity.”

Yet, the median age for elective egg freezing is 38.2.