Egg freezing

Fertility rates in developed countries are falling, mainly because women are choosing to delay having children as their careers take off.

That means many women are making a tradeoff. Oocytes (more commonly known as eggs) are a limited resource. For many people 38 or older, their eggs are less likely to be normal, making it difficult or impossible to become pregnant.

But by harvesting eggs from the ovaries en masse at a younger age and freezing them, women can plan on using their young, healthy eggs when they’re older, increasing the chances that they can have a child later if they want to.

In 2017, nearly 11,000 women in the US chose to freeze their eggs, up from fewer than 500 in 2009. It’s an expensive and imperfect process—but that’s not stopping a young, feminist workforce from demanding a chance to have a family on their own timeline. Let’s explore this fertile subject.

6-7 million: Fully formed eggs present in a female fetus at 20 weeks of gestation

300–400: Eggs adult ovaries will ovulate in a person’s lifetime

5–12: Eggs that can be retrieved per cycle, on average; it can be up to 45, but this is rare

25: Eggs fertility specialists recommend people try to freeze if they can

$15,000–$20,000: Average cost of a single egg-freezing cycle.

$6,500: Cost of one cycle of egg freezing at Kindbody, which uses largely digital technology to lower costs (excluding costs of medicine)

4%–12%: Chances of creating a successful pregnancy per egg

70%–90%: Chance a person 35 or younger who freezes 10–20 eggs has of having a healthy baby later in life

A class of medications called gonadotropins can cause the ovaries to mature and release multiple eggs. A person freezing their eggs will take these medications for a week to 12 days, followed by an injection of human chorionic gonadotropin to release all of them at once.

At a fertility clinic, a clinician will insert an aspirator through the vagina into a follicle to remove the mature eggs. Once they’re safely in the lab, it’s time to freeze them.

Egg cells are largely water, and they have a shell like a chicken egg. The biggest difficulty of egg freezing is preventing the water from expanding as it gets cold and cracking the shell.

Embryologists use the process of osmosis to remove water out of the egg, and insert a sort of cellular anti-freeze that prevents the shell from cracking. After that, they’ll fast-freeze the egg in liquid nitrogen where they can be stored indefinitely.

1948: Experimenting with the cryopreservation of chicken sperm, Christopher Polge accidentally discovers that glycerol is an effective medium, the result of a mislabeled bottle.

1951: Frosty, the first calf from frozen sperm, is born.

1953: The first experiment in oocyte freezing, using rabbit eggs, is attempted.

1973: Frosty Two, the first calf from a frozen embryo, is born.

1978: The first baby is born via in vitro fertilization (IVF) in Bristol, England.

1984: The first baby is born from a frozen embryo in Australia.

1986: The first person conceived with a frozen egg is born, in Melbourne, Australia.

2007: The first baby is born from frozen, lab-matured oocytes.

2010: Robert G. Edwards wins the Nobel prize in medicine for his work on IVF.

2012: The American Society of Reproductive Medicine declares that egg freezing is no longer an experimental procedure.

2017: A baby is born from an embryo frozen for 25 years.

“I’m paying for peace of mind. To be able to make decisions not based on my biological clock. If there’s even a 1% chance I could potentially have a child if I couldn’t have one otherwise, I will take that a thousand times over.”

—Valerie Libby, a 34-year-old studying to be a fertility specialist and has frozen her eggs, to the New York Times

After a person undergoes egg retrieval as part of IVF, the eggs are fertilized with sperm in a petri dish. Over the course of 96 hours, the cells in the embryo double, until there are 128 or more. At this point, the embryo is called a blastocyst. About half of the cells in the blastocyst will go on to become the fetus itself, while the other half will become the placenta.

These embryos can be transferred into the uterus. Usually, doctors will wait for an ovulation cycle before transferring an embryo into the uterus. During this waiting period, the embryos are frozen using a similar process to egg freezing. Ones that are not transferred can remain frozen for future pregnancies theoretically indefinitely. They can also be donated to other hopeful families trying to expand, donated to science, or discarded.

We’ve given you the science side of things—but then there’s the practical side. What’s egg freezing actually like? You have to give up booze and intense workouts for how long? Nicole Ellis explains for the Washington Post.

Egg freezing can play a critical role in fertility care for the trans community—specifically trans men. If an adult wants to begin taking the hormone testosterone (which is not a requirement to transition) to appear more masculine, they can choose to freeze their eggs ahead of time so they don’t have to ever stop taking testosterone if they don’t want to. If a person has been taking testosterone as part of their transition and still has their ovaries and uterus, they’d need to discontinue taking it for roughly six months before they could try to become pregnant.

Because the trans community has been excluded from most medical research, reproductive specialists serving this community have had to learn from cancer treatment. Egg freezing can preserve fertility for those who have been diagnosed with cancer, if they can delay their treatment for long enough to go through an egg retrieval.