In 1970, the average woman in the U.S. had her first baby at around 21 years old. That’s hard to imagine now: new federal data published in April show that in 2022, the average first-time mother was a little older than 27—a record high for the country, and a sign of a major demographic change.

This shift has been underway for years. Teenagers and women in their early 20s are having fewer kids, while the opposite is happening among older age groups. In 2022, for the seventh year in a row, the birth rate among U.S. women in their early 30s was higher than the rate among those in their late 20s. Perhaps even more notably, the number of babies born to women 40 and older, while still low overall, rose considerably from 2021 to 2022: up 6% among women ages 40 to 44 and 12% among those older than 45.

Dr. Florencia Polite, chief of general obstetrics and gynecology at the University of Pennsylvania’s Perelman School of Medicine, says those data track with what she sees in the clinic: U.S. parents are getting older. “This is the first time I’ve had three patients who are pregnant in their 50s,” she says.

The foundation for this trend was laid in the 1960s, when the birth control pill came onto the scene and gave women unprecedented control over their fertility, says Aurélie Athan, a clinical psychologist who researches the psychology of motherhood and reproductive identity at Columbia University’s Teachers College. In the decades since, it has become increasingly common for people to have children later in life for a range of reasons, including concerns about finances and child care, waiting longer to get married or find a partner, and prioritizing education, career, or leisure time during young adulthood. The decision to stay child-free has also become less stigmatized, Athan notes, and some data suggest more people are taking that route.

“Women are having a pregnant pause,” Athan says. “They’re really taking time to say, ‘Do I want to do this?’”

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It’s not just women. Research suggests many young men are also thinking deeply about when and whether to have kids, says Karen Guzzo, a family demographer at the University of North Carolina at Chapel Hill.

But waiting doesn’t always mean people aren’t enthusiastic about eventually having children. Guzzo found in a 2023 study that it’s still far more common for people to want children than to plan to stay child-free, and that most prospective parents want more than one baby. What’s different from decades past, Guzzo says, is that people are increasingly pushing back the ages at which they have those kids, often into their 30s and beyond.

That can be a gamble. In a 2018 New York Times survey, about 25% of respondents said they had or expected to have fewer kids than they originally wanted, often because they couldn’t afford or ran out of time to have their ideal number of children. People of color in the U.S. often say they want large families but end up with smaller ones, Guzzo notes—a sign that not everyone is able to achieve their ideal scenario.

“What I really worry about,” Guzzo says, “is that we’ve become a country where some people get to have the kids that they want and some people don’t.”

In some ways, delayed parenthood is a sign of progress. Waiting to have kids is a kind of empowerment for some women, ensuring they can finish their education, find a fulfilling job, become financially stable, choose the right partner, and grow and mature as a person before settling down to have a family. Some studies suggest that kids born to older parents—who tend to be college-educated and relatively affluent—often grow up to be healthier, better educated, and better behaved than peers with younger parents, and that women who have children later in life report bigger happiness boosts around and after their birth, compared to younger mothers.

Untangling why people feel they need to be educated, financially secure, and partnered before having kids is more complex. For many people, it’s related to societal expectations—many rooted in class and race hierarchies—about what makes a “good” parent, research suggests. For others, it comes down to cold, hard math. Child care is prohibitively expensive in the U.S., paid parental leave isn’t guaranteed, and living costs are sky-high in many places. Those structural barriers cause some people to postpone having kids by necessity.

Some people who wait to have kids, whether by choice or circumstance, may find that they’ve waited too long. Fertility begins to decline around a woman’s 30th birthday and starts to drop more dramatically around age 35. By the time a woman turns 45, the American College of Obstetricians and Gynecologists says, it’s very unlikely she’ll get pregnant naturally. (Although some men father children well past middle age, their fertility also declines with time.)

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Enter the world of assisted reproductive technology, where demand for services like egg freezing and in vitro fertilization (IVF) is booming. As of 2023, 42% of Americans said they or someone they knew had used fertility treatments, up from 33% five years earlier. That growing popularity—and the hefty price tags attached to these services—have made it a multi-billion-dollar industry in the U.S.

These scientific advances have allowed some people to have children who otherwise couldn’t because of fertility issues, age, or life circumstances. In 2021 alone, almost 100,000 U.S. infants were born using these methods. But they’re not accessible to everyone: a single IVF cycle can cost well over $10,000, and it may not be covered by insurance.

Even for people who can afford that price tag, it’s not a guarantee. In 2020, about 37% of assisted reproductive technology cycles undertaken in the U.S. resulted in a baby, meaning the majority of people either needed multiple cycles or did not end up conceiving. And as with natural conception, success rates decline with age, a cruel fact that means people who use fertility treatments as an insurance plan sometimes still face an uphill battle. Technology allows a woman to “stretch” her reproductive window, Athan says, “but it’s still not elastic as maybe we’ve internalized.”

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Studies also show that the risks of pregnancy and birth complications—such as gestational diabetes, high blood pressure, preeclampsia, and miscarriage, plus low birth weight and genetic disorders in babies—rise with age. But as medical care advances and social norms shift, some women are pushing back on the idea that older mothers are automatically putting their health, and the health of their baby, in danger.

Some doctors agree. Labels like “geriatric pregnancy,” once applied to all mothers 35 and older, seem outdated at a time when birth rates are exploding among people in that age group. The more common medical term now is “advanced maternal age,” but some doctors are reevaluating who fits into that category, says Polite, from the University of Pennsylvania. “The truth is, a lot of women from 35 to 40 are not really considered high-risk anymore,” she says. With the testing methods and research available today, she says, it’s pregnant women in their 40s and 50s to whom she pays closest attention.

Dr. Lisa Dunn-Albanese, an ob-gyn at Brigham and Women’s Hospital in Boston, agrees that it’s become routine to see older parents in the clinic, and that most of them have healthy pregnancies. “I’m not too worried, I have to admit, about my 30-year-olds,” she says. Age is often a less relevant risk factor than something like an underlying health condition, she adds.

To Dunn-Albanese, the data on delayed motherhood isn’t overly concerning, at least from a medical perspective. But what it says about who is waiting to have kids and why, and the resources available to them when they do, is a more complex question, Guzzo says.

“We might be settling into this new, lower fertility rate where people are waiting longer to have kids,” which is not inherently a bad thing, she says. What’s more concerning, in her eyes, is the reality that not everyone who waits does so by choice, and that postponement can turn into not having children at all.

“This is a pretty basic thing,” Guzzo says. “If people want to have children someday and they can’t, that’s an indictment of how our society is structured.”