Rita hadn’t planned on having kids until she was finished with her post-medical school residency. When the subject of children was first broached, she and her husband were still completing their residencies at the University of Utah—for surgery and neurology, respectively. That meant a lot of long hours and sleepless nights. No need to add a baby on top of that, they decided. Plus, Rita (not her real name) would only be 31 when they finished the program. That left plenty of time, conventional science says, to start a family. Rita, I should mention, was my longtime penpal—we met at camp when we were 11, and continued corresponding well into college. She was always the more driven one, the better planner.

Yet when we were both 28, I received an email from Rita with an attached photograph showing two pairs of cowboy boots standing on a wooden fence. Between the boots perched a pair of tiny, knit booties. “There’s a new cowpoke riding into town...” read a banner at the bottom of the photo.

I wrote back, asking Rita what happened. Her response: “I went to see my OB/GYN on January, and after my exam, she asked if there was anything else she could do for me. I jokingly replied, ‘No, unless you can tell me how many years I have left to get pregnant!’ And she said, ‘Well ... there is this one test.”

The answer, the doctor explained, lay in an experimental procedure called an anti-Müllerian hormone test. It’s a blood analysis, just like a cholesterol check, but it measures the amount of anti-Müllerian hormone a woman has circulating in her bloodstream. The idea is that a low result could mean an otherwise healthy woman’s window of fertility is narrower than most, and that she should take action right away, whether it’s starting baby-making, or harvesting her eggs to freeze for the future.

So what started with a joke led to the photo of mini-cowboy boots hovering on my computer screen. And for me, this was just the beginning: I took my own anti-Müllerian hormone test, and I researched and wrote this story. To my co-workers, I claimed curiosity at the test’s effectiveness. But deeper down, I really wanted an answer to what could convince a woman—a doctor; my coolheaded, uber-planner friend—to push her baby-making deadline up so drastically. Surely not some test with only an emerging glimmer of supporting scientific evidence?

It’s hard to say exactly how many doctors offer their healthy, young patients anti-Müllerian hormone tests, the way Rita’s did. The test is more often used for women who already know they’re struggling with infertility; after trying with no success to get pregnant for six months or a year, they’ve decided to start in vitro fertilization. In those cases, there’s increasing evidence that the test can indeed predict how well a woman will respond to egg harvesting treatments.

It’s less certain what an anti-Müllerian hormone test might offer a woman who’s never tried to get pregnant. Anti-Müllerian hormone levels are a direct measure of the number of eggs a woman has, which is an important part of her fertility. But scientists are just beginning to take a deeper look at whether the results of their anti-Müllerian hormone tests correlate with trouble getting pregnant. Beyond that, doctors must jump through several logical hoops to turn an anti-Müllerian hormone test result into advice for aspiring moms-to-be.

Still, if you’re interested, the test is out there. I called fertility clinics in Seattle, Salt Lake City, and suburban Connecticut, and they all confirmed offering the test to young, often single, women, many of whom have never tried to get pregnant, and in fact have no idea if they’re infertile. “We do it all the time,” says Angela Thyer, a founding doctor with Seattle Reproductive Medicine. “We call it, like, a fertility assessment.”

In Rita’s case, her anti-Müllerian hormone test turned out “abysmally low,” as she puts it, so “we figured we should have the kid ASAP.” She became pregnant in the spring of 2013, during her third year of residency, and, in spite of her low results, had no trouble conceiving.

A test like this has been a long time coming. Although plenty of good science exists indicating at what age most women are likely to start having more trouble conceiving, researchers have long known many women would prefer their own personalized baby deadlines. In the past, scientists tried creating such a test from a number of different hormones. The anti-Müllerian hormone, says University of Edinburgh reproductive scientist Richard Anderson, is just the “current frontrunner.”

To understand the anti-Müllerian hormone test’s promise and limitations, you need to know a little about its science. Anti-Müllerian hormone is produced by the small, growing follicles in the ovaries. These follicles are tiny, liquid-filled capsules, in which human eggs mature. Measuring how many growing follicles a woman has—or at least, how much anti-Müllerian hormone they make—is a measure of how many eggs the woman has left. It’s a bit like estimating how many blown dandelions are in a field by measuring the number of seeds floating in the air.

Researchers think the natural, falling fertility rates women experience as they age comes from losing both egg quantity and egg quality. That is, a woman becomes less fertile with time in part because she doesn’t have many egg-producing follicles left. She starts with a little under half a million when she hits puberty, then loses something on the order of 10,000 per year until, at some point, she reaches menopause. At the same time, women also become less fertile with age because their remaining eggs have had more time to accumulate DNA damage. So the anti-Müllerian hormone test deals with the first half of this equation.

The test offers a fairly direct measure of a woman’s ovarian reserve. The only more direct option would be to go straight to the source—to get a (far more complicated and expensive) 3-D ultrasound, which allows doctors to count the follicles in a woman’s ovaries.

There are some caveats, however. Unlike an ultrasound, an anti-Müllerian hormone (or AMH for short) test result doesn’t tell doctors how many ovarian follicles a woman has because scientists don’t know enough yet to be able to convert an AMH amount into a follicle number. So as a workaround, doctors compare a woman’s AMH level with a chart of average AMH levels in women of different ages. “Low” and “high” results are relative to other women of the same age.

Clinics that offer AMH tests as fertility predictors use low results as evidence that a woman should freeze her eggs soon. But there’s a problem with that: There aren’t actually any studies that say what a woman’s anti-Müllerian hormone levels now mean for her future, though researchers are working on it.

Age is still the scientifically soundest predictor of how much time a woman has left. Every researcher I spoke with emphasized this. Yet humans vary so widely, it’s easy to imagine your situation may be different from the average. And you don’t want to know when the average woman is out of time. You want to know for you.

Why is the anti-Müllerian hormone test so popular now, even with all of this uncertainty? Why not wait until we have more evidence?

Because, as Rita says, “it’s the best we have.” It provides at least an answer.

The test seems to have gained in popularity alongside the rise of egg freezing, which the American Society for Reproductive Medicine declared no longer “experimental” in 2012. But not everyone supports linking AMH results with egg freezing. “There’s not a lot of data to help guide somebody as to whether or not they should do that,” says Anne Steiner, an infertility doctor and professor at the University of North Carolina School of Medicine. “We don’t know [how to answer a question like] ‘OK, my AMH level is this, should I freeze my eggs because two years from now I’m not going to have any eggs?’ I don’t think we know what’s going to happen to people two or three years down the road.”

I talked with one woman, Alyssa Sperber, who took the test—and froze her eggs—when she was 34. She’d been asking her regular gynecologist about her fertility, after seeing magazine articles about how women generally have a lot of trouble conceiving after 35. Sperber was single at the time and “didn’t necessarily have a prospect in sight.”

Her gyno referred her to the Reproductive Medicine Associates of Connecticut, a group of five fertility clinics. RMA of Connecticut works to get the word out to gynecologists about their fertility assessment services. RMA also holds quarterly fairs, where they offer the anti-Müllerian test to locals for free.

In addition to her anti-Müllerian hormone test, Sperber took a follicle-stimulating hormone test and an ovary ultrasound. The results of the anti-Müllerian hormone test and the ultrasound were troubling. For AMH, she says, “I was in the almost undetectable range, I was so low.” She’ been considering freezing her eggs before; that provided the kick she and her doctor needed to go ahead with the procedure. “Once I got that AMH back, I had to do everything to get those eggs out of me, now,” she says.

Not long after Rita had a healthy baby boy, I got my own anti-Müllerian hormone test. By that time, I had researched and written most of this article. I had to take the test. I was too curious.

The process was swift and easy. While I had my blood drawn, I chatted with the nurse practitioner, who told me about her 31-year-old daughter who was, she sighed, still single. The nurse had started encouraging her daughter to consider freezing her eggs.

I got a call five days later from the doctor. Before I took the test, I’d assumed I wouldn’t care if I found a low result, one that my doctor called “weakness, or ovarian compromise.” Yet, after I hung up, I felt an overwhelming relief. I don’t want to have children now, not for several years at least, and I can’t afford egg freezing.

Although I never told Rita I was thinking of taking the test for this story, she sent me a warning anyway. In an email, she wrote, “If we weren’t thinking about having kids or not in a position to have kids (i.e.: not in a long-term relationship, not married—if that matters to you) there is no point to get the test. (Well, other than to freak you out?)”

Things may be different in the future, if studies establish the anti-Müllerian hormone test, or another hormone test, to be truly predictive. As it stands now, the only thing the test can tell you is whether to panic, and to take drastic action. Even then, because of the uncertainty surrounding the test, you can’t know for sure if you acted on good intelligence.

Rita and Alyssa Sperber aren’t plagued with such worries. “The old adage ‘There is no good time to have kids’ always holds true,” Rita says. “Also the saying how nobody ever feels ready to have kids. We just bit the bullet and did it.”


Welcome to No One’s Watching Week, the time of the year when the readers are away, and your tireless editors have run amok. For this week only, Atlas Obscura, the New RepublicPopular MechanicsPacific Standard, the Paris Review, and Mental Floss will be swapping content that is too ​out there​ for any other week in 2015.