How Did Hilary Swank Get Pregnant at 52? It’s Not Hard to Understand, if You Know a Little About Biology.

Sign up for the Slatest to get the most insightful analysis, criticism, and advice out there, delivered to your inbox daily.

Hilary Swank recently revealed on Instagram that she is pregnant with her third child. Nothing especially weird about that—celebrities do pregnancy reveals on social media all the time. Except for one thing: Swank is 52 years old. Having a baby at that age is quite rare, to put it lightly.

Given her age, she almost certainly used IVF. My family is only possible via IVF, too—I’m delighted for her. There’s nothing worse than wanting kids and not being able to have them. It’s a unique form of torture that anyone who’s been to a fertility clinic will know all too well.

But as an epidemiologist, I do have a question: What are the chances? And why does it suddenly seem like celebrities everywhere are getting pregnant at older and older ages?

Most people are aware that reproduction is sexist. Men can contribute to babies well into their 80s—yes, sperm quality declines but not that much—while the ability to get pregnant is pretty much capped at age 45. There are very rare reports about people getting pregnant in their late 40s, but data shows that this is far from the norm. A 2020 review that aggregated data on 4,379 women over age 35 who were trying to get pregnant via natural conception found a 12-month pregnancy rate of 25 percent at ages 35–39, which fell to 10 percent by age 43.

IVF does improve these numbers somewhat, but the decline is still steep at older ages. The pregnancy rates might be as high as 15 percent at age 43, depending on what data you are looking at. But I could not find a paper with a pregnancy from IVF over the age of 44. Even at 44, the rate is extremely low.

That is, it’s low if you go through the full process of having your eggs retrieved at 44, fertilized, and then an embryo implanted. You can up your chances significantly if you’re working with younger eggs. Swank froze hers at age 37. Freezing your eggs is an expensive procedure that costs somewhere in the region of $20,000 per retrieval. Many people have to do two to three retrievals, because there’s no guarantee of getting enough eggs the first time, especially if you’re freezing them in your late 30s.

If you’re using frozen eggs, the chances of getting pregnant aren’t bad at all. A recent massive study from Australia and New Zealand found that even at older ages, the pregnancy rate was around 40 percent for women who froze and then thawed their eggs regardless of how old they were when they thawed the eggs. The only thing that mattered was how old they were when the eggs were frozen. Younger was better. Younger eggs are more often genetically normal, and therefore result in more healthy embryos (which are more likely to result in a viable pregnancy) than eggs collected at older ages. Also, you tend to get more eggs when collecting them younger as you’ve got a larger reserve in your ovaries.

This holds for donor eggs. A national study from the United States found that pregnancy rates for women over the age of 40 using donor eggs was pretty similar to rates at younger ages. There was a decline after the age of 50, but it wasn’t huge. At age 30, 57 percent of women who used donor eggs had a successful pregnancy, which fell to 49 percent above age 50.

There are some downsides to getting pregnant at older ages. You’re much more likely to experience problems like preeclampsia and gestational diabetes. The miscarriage rate—even with frozen or donor eggs—starts to climb as you get older. It can also get extremely expensive. Even ignoring the costs of egg retrieval in your 20s or 30s, the costs of treatment rise dramatically with age: You need more injections and more scans, and you need much closer monitoring by a medical team. The exact cost is going to vary depending on where you go and how many implantations you have to do, but it’s easy to imagine the price tag being over six figures just to get pregnant.

In other words, it’s not impossible to get pregnant well into your 50s as long as you have quite a lot of money. It’s a bit more dangerous than having a baby at a younger age, but not drastically more worrisome. If you’re a wealthy celebrity who had the foresight to freeze your eggs—or who wants to use an egg donor—it’s an expensive but relatively simple route to parenthood.

Given the exorbitant cost, I doubt we’ll see a wave of pregnancies later in life. But we should expect to see the occasional celebrity gender reveal even for women in their late 40s and 50s. It’s not easy, but with a lot of money and a bit of luck, it’s possible to get pregnant well after you’ve hit 45.