Pregnancy linked to faster aging, new research suggests

But one of the studies also suggests this process may reverse itself once a woman gives birth, rewinding time so that some mothers’ cells seemingly end up biologically younger afterward than they’d been during gestation, especially if a mother breastfeeds her baby.

Together, the studies underscore how physically demanding pregnancy is. But they also raise important questions about aging itself and whether it really can be sped up, slowed or reversed by pregnancy.

The newest of the studies, published today in Proceedings of the National Academy of Sciences, found pregnancy “has a big impact on a woman’s body” and biological age, said Calen P. Ryan, an associate research scientist at the Columbia Aging Center at Columbia University in New York, who led the new research.

In it, scientists used several different biological-age “clocks” and other measures to analyze DNA markers in blood samples. These clocks aren’t timepieces but, instead, algorithms, developed using artificial intelligence programs, that examine the patterns of specialized chemical markers found on the outside of some genes. These markers accumulate and change in response to our age, health and lifestyles, a process known as epigenetics.

The algorithms can use these epigenetic markers to estimate the relative age of cells. This measure, often referred to as biological age, can differ from someone’s chronological age, which just means how long he or she’s been alive.

In the new study, the researchers checked blood samples from 825 young women in the Philippines, all born in the same year. Some had been or were pregnant, and others hadn’t conceived. Analyzing these samples, the epigenetic clocks broadly agreed that the biological age of the young women who’d been or were pregnant tended to be higher than that of the others, by at least several months, even after the researchers controlled for economic disparities and other social and health factors.

Pregnancy as a stress test

Similarly, the other new study, published in March in Cell Metabolism, used several different epigenetic clocks to estimate the changing internal age of pregnant women at several points during their pregnancies.

“We were very interested in looking at the impacts of pregnancy as a naturally occurring stress test,” said Kieran J. O’Donnell, an assistant professor at the Yale Child Study Center and Yale School of Medicine, who oversaw one of the new studies.

With blood samples from 119 pregnant American women and five different clocks, the researchers tracked the epigenetic changes related to the women’s biological age, starting early in gestation and ending three months after they’d given birth.

The clocks again agreed that pregnancy seemed to be aging the incipient moms as they approached full term, making their blood cells’ DNA appear to be as much as two years older than it had been earlier in the pregnancy.

More encouraging, though, O’Donnell said, is that this aging seemed to reverse for most of the women within three months after birth. In general, their patterns of DNA markers soon reverted to an earlier, more-youthful state, and for some new moms who’d breastfed exclusively in the first three months postpartum, overshot the mark, leaving them apparently “younger” biologically than before, by as much as eight years, the study’s authors wrote, “indicating a pronounced reversal of biological aging.”

But some researchers who study aging, longevity and epigenetics are skeptical of the studies’ findings and conclusions. “It seems unlikely to me that pregnancy induces a whole-body acceleration of biological aging which is then reversed soon after pregnancy,” said Matt Kaeberlein, a longtime longevity researcher who serves as CEO of Optispan, a company that promotes longevity and produces the “Optispan” podcast.

Charles Brenner, who studies metabolism, cancer and aging at the Beckman Research Institute of the City of Hope National Medical Center in California was blunter in an email. “100%, it’s a misuse of aging biomarkers,” he wrote.

Both scientists, as well as others who’ve discussed the studies online, speculate that the epigenetic shifts seen during pregnancy probably reflect the profound physiological demands of carrying a child. They’re “a transient response to the stress of pregnancy, particularly in the immune system,” Kaeberlein said.

What they aren’t is evidence that pregnant women suddenly get older and then younger, these researchers say, or experience lasting effects that could directly shorten or lengthen their life spans.

But the cellular changes being picked up and analyzed by the epigenetic clocks might someday be useful health indicators. If a pregnant woman’s epigenetic markers don’t soon bounce back once she’s no longer pregnant, she and her doctor might want to closely monitor her blood pressure, blood sugar and other standard measures of health, not because she suddenly seems older after becoming pregnant, but because, Ryan said, “pregnancy is such a big deal, physically.”

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