Women who can become pregnant without procedures like fertility treatments in their mid-30s and beyond are also the women most likely to live to a very ripe old age, according to new research.
The study by Boston University researchers was published in Menopause, the journal of the North American Menopause Society.
"Among their study group of 462 women in the United States and Denmark, women who had their final child when they were 33 or older were twice as likely to live especially long (defined as living longer than 95 percent of the women in their demographic group), compared to women who were finished having children by 29," wrote Vox's Joseph Stromberg.
"But having a child at a late age is a marker of a long lifespan — not a cause of it," he wrote.
"The current findings suggest that prolonged fertility may be linked to a genetic marker for longevity, though a marker hasn’t yet been identified," Dr. Thomas Perls, a co-author of the study, a professor of medicine at Boston University School of Medicine and the director of the New England Centenarian Study, told the Boston Globe.
In a press release, he said that “the natural ability to have a child at an older age likely indicates that a woman’s reproductive system is aging slowly, and therefore so is the rest of her body.”
The researchers looked at women who had lived longer than 95 percent of their peers, comparing them to women who had lived an average lifespan. After controlling for factors like tobacco use, family size and other things, they found the women who lived a long time were more likely to have had a child after age 33.
The effect was not as strong as belonging to a family that was known to consistently live to old age, but it was still a "significant association," the study authors said.
"Perls stressed that women should not take the study findings and purposely delay when to have their children," wrote Lena H. Sunn of the Washington Post. "Researchers don’t know if any of the offspring in the study had congenital problems. Doctors generally advise women that the risk of congenital problems increase with the older age of the mother.
“In our case, these are all women with longevity running in their families, so we don’t know if it’s the same risk or not,” Perls said.
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