Fertility banking allows women to flex their biological clocks by freezing their eggs and embryos until they’re ready to build their family.

The practice is exploding. From 2010 to 2016, as reproductive medicine began endorsing freezing eggs and embryos, the practice jumped by more than 880% in the U.S. Approximately 7,440 embryos were banked in 2021, up from 5,380 the previous year, according to the Society for Assisted Reproductive Technology. In the same time period, egg banking grew from roughly 16,790 eggs frozen to 22,270, and preliminary figures from 2022 show a jump to more than 29,000 eggs.

Fertility banking is also on the rise in California. At Cedars-Sinai, about one-quarter of fertility patients chose to freeze their eggs or embryos prior to 2020. Today, one-third opt for the tactic.

Cedars-Sinai specialists expect the approach to continue gaining traction and changing how women have children.

“It gives women more choices and more control over their reproductive health,” said Reproductive Endocrinology and Infertility Clinic Director Erica Wang, MD.

Read: What You Need to Know About Your Fertility

If you opt to freeze your eggs, you will undergo 10 to 12 days of hormone injections to stimulate your ovaries to grow a cluster of eggs. Your doctor will check on their development using ultrasounds and blood tests.

When your eggs are ready, the clinic will retrieve them through the vagina at a same-day surgery center while you are under anesthesia, and the eggs will be frozen (cryopreserved) right away.

Embryo banking adds an extra step. In the lab, specialists will fertilize your eggs with sperm, allow the embryos to mature over five to seven days, and then freeze them.

Later, if you want to try to get pregnant with your frozen reserve, the lab will thaw your eggs or banked embryos. Eggs will be fertilized to become embryos, and your doctor will transfer embryos into your uterus.

Once considered experimental, egg freezing has come a long way.

Technological advances during the past decade—especially the move from a slow-freeze method to a flash-freeze method (vitrification)—help providers better protect and preserve the eggs. The faster freezing method limits the formation of ice crystals, allowing a much higher rate of thawed eggs (95% versus 70%) to survive, according to Wang.

“It’s not a guarantee for the future, but it is the best option we have,” Wang said.

For women under age 35—who have the best chances of getting pregnant using frozen eggs—each egg has about a 5% likelihood of resulting in a pregnancy. Some eggs don’t fertilize or implant correctly, so women may undergo multiple embryo transfers to conceive from the available supply. Typically, depending on the age at which the women froze their eggs, around one-third of women who use them will have a baby.

Wang added that awareness of the technology has spread, encouraging a new generation of women to consider freezing their eggs or embryos for later.

And as fertility treatments become more mainstream, private insurance companies in California are increasingly covering them—though most still don’t—driving demand for the services even higher.

Read: Do Fertility and Ovulation Apps Work?

Women are born with a complete set of around 1 million to 2 million eggs. Although everyone’s reproductive systems are different, a woman’s egg stockpile and its quality typically dwindle over time, gradually at first, then with a steep drop-off around age 37.

That means assisted reproductive technology can be valuable, for example, to a single 30-year-old who doesn’t plan on getting pregnant soon but would like to eventually, or a 35-year-old parent who wants to have a third child.

Women in their early 40s have a lower success rate with fertility preservation. Experts recommend they bank frozen embryos, rather than eggs, to conceive.

This method is growing in popularity and quickly catching up to egg banking.

Wang encourages anyone thinking about building a family to speak with their primary care doctor or OB-GYN for a referral to a reproductive endocrinologist. The specialist will start with a full consultation and then test the patient’s egg reserve and other fertility measures (such as hormone levels).

“Freezing can help ensure you have children,” Wang said. “But we have to remember that, unlike other insurance that you can count on to pay out if something goes wrong, we won’t know the outcome unless we use the frozen eggs or embryos.”

Read: Your Fertility and Your Future

What is the ideal age to bank? Wang recommends beginning the process at between 30 to 35 years old.

When cryopreservation first started, women were requesting it a little too late, she said. Patients are skewing younger, though, since it’s become more common.

You may need more eggs frozen if you’re older. In an analysis, the American Society for Reproductive Medicine points out that to reach 70% likelihood of giving birth, 30- to 37-year-olds need 14 to 15 preserved eggs, while 38- to 40-year-olds need 26 preserved eggs.

To figure out your options, reproductive endocrinologists will consider your age alongside your egg supply, sperm access, goals (such as how many children you want) and medical history.

People with a complex medical history should know that fertility banking has some risks. In particular, the risk from high estrogen exposure needs to be addressed if you’re susceptible to hormone-driven conditions, such as breast or endometrial cancers or blood clots.

During the process, Wang treats her patients as if they were already pregnant, starting them on prenatal vitamins and encouraging a healthy lifestyle. She also suggests limiting alcohol and caffeine, adopting a nutritious diet, and getting moderate exercise.

The key is to empower yourself in your childbearing journey, whatever that means for you.

“It’s a proactive decision to plan ahead for pregnancy,” she said.

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