Olivia Munn and John Mulaney froze embryos in hopes of having another baby after her breast cancer diagnosis. Here's how the process works during treatment.

Olivia Munn is sharing more about her treatment for breast cancer in a new interview with Vogue. The 43-year-old actress — who was diagnosed with an aggressive form of breast cancer called luminal B in February following a risk-assessment test — told the magazine that she has undergone a hysterectomy as part of her cancer treatment, which has also included a double mastectomy. Munn said confronting how cancer treatment could affect her fertility prompted her and partner John Mulaney — already parents to 2-year-old son Malcolm — to have a frank conversation about the future of their family.

“We decided to try one more round of egg retrievals because John and I talked about it a lot and we don’t feel like we’re done growing our family,” the former Newsroom star said. While Munn had previously had her eggs frozen, at age 33 and again at 39, she and Mulaney wanted to increase their chances of having more children, with the help of a surrogate.

“We just wanted a few more eggs,” Munn told Vogue. “At my age, one in every 10 eggs are healthy, and we were hoping to make one embryo from this retrieval.”

In a follow-up interview with Good Morning America on Thursday, Munn shared that she and Mulaney were ultimately able to create two healthy embryos. "We really just hope that it works out for us to be able to have another baby," she said. "We just want one more."

Undergoing assisted reproductive technology during cancer treatment isn’t without challenges. Here’s what to know about preserving fertility during the process.

What is embryo freezing?

Embryos are eggs that have been fertilized with sperm. As with egg freezing, the first step in the process of freezing embryos is to give a woman hormone injections (usually over the course of about 10 days) to prompt the ovaries to make multiple eggs in a single menstrual cycle. Another drug prevents ovulation, the process by which an egg is released from the ovary into the fallopian tube, where it would normally wait for fertilization, Dr. Kara Goldman, a reproductive endocrinologist and infertility specialist at Northwestern University, tells Yahoo Life.

Instead, doctors then use a minimally invasive procedure involving a long needle and suction to gently extract the eggs from the ovaries. After that, the eggs themselves are either frozen, or fertilized with sperm (becoming embryos) and then frozen. The embryos can also be tested to be sure they’re sufficiently healthy and viable before freezing. Embryos can remain frozen for at least 10 years, according to Johns Hopkins Medicine.

How is the treatment different for cancer patients?

Some cancer treatments, including chemotherapy, can affect fertility. “Even if you’re not having chemo, in anyone with an estrogen-positive tumor, like [Munn] has, there’s long-term ovarian suppression,” says Goldman. Ovarian suppression prevents the ovaries from making estrogen and fueling tumor growth, and can be done with medication or surgery to remove the ovaries. Munn initially tried medication but ultimately opted for surgery. “If a patient needs chemo they have two hits to their fertility: They’re at risk of loss of fertility due to chemotherapy and [also] due to time,” because fertility declines with age and may be lower by the time someone finishes treatment, Goldman explains.

“It is extremely common for reproductive endocrinologists to work together with oncologists and patients to create a window to preserve fertility,” Dr. Alan Copperman, director of the Division of Reproductive Endocrinology and Infertility at the Mount Sinai Health System, and CEO and managing director of RMA of New York, tells Yahoo Life. Dr. Christine Mullin, chief of fertility at Northwell Health, estimates that about a third of young women are still hoping to have children at the time they’re diagnosed with breast cancer.

The embryo freezing process is largely the same, but for people with estrogen-fueled forms of cancer, like Munn’s, there may be some modifications. The hormone therapy used to stimulate the ovaries to produce more eggs can lead to estrogen spikes, so it’s often given at lower doses, Goldman says; this was the case for Munn, according to her Vogue interview. Doctors may also use an additional medication to keep blood levels of estrogen lower so they don’t lead to tumor growth or progression.

Are there any risks?

“There are a few important risks and experiences that the patient needs to know about” before starting the egg- or embryo-freezing process, whether or not they have cancer. Goldman says. The hormone injections used to ramp up egg production can cause ovarian hyperstimulation syndrome, which can cause the ovaries to swell painfully and leak fluid into the pelvis, abdomen and even around the lungs, according to Cleveland Clinic.

Exercise should also be avoided during the 10 to 14 days of treatment, to prevent ovarian torsion, or painful twisting of the organs. The procedure to extract the eggs, though minimally invasive, also comes with the risk of infection.

But, generally speaking, the egg- or embryo-freezing process is safe, and for cancer patients “the [cancer] treatments they’ll be facing are much riskier, so this is often one of the easier portions of treatment” from a physical standpoint, says Goldman. “I say that with a caveat, because nothing about treatment and going in for testing every day when you’re facing a cancer diagnosis is easy; patients may feel fatigued because of the fluctuation in hormones, but they’re also likely fatigued coming into the office for monitoring so frequently.”

What’s next?

While outcomes vary, Goldman notes that embryo freezing gives a patient more “certainty” of their odds of having a baby. That’s particularly important for cancer patients, who can’t afford the time it takes to do multiple retrievals before undergoing chemotherapy or other treatments.

“The fact that [Munn and Mulaney] have two healthy, tested embryos will give them a 60 to 70% chance at a live, healthy birth” with the help of a surrogate, says Goldman. “She was very fortunate to have that outcome.”

This article was originally published on May 13, 2024 and has been updated.