Expecting or Planning? There’s Nothing Magic About Age 35.

Many of the decisions I made around my pregnancies were based on the looming specter of “advanced maternal age,” which is typically defined as 35 or older. Rudely, this used to be called a “geriatric pregnancy,” but that term is thankfully now out of fashion. In my head, my 35th birthday was some kind of Cinderella clock, but instead of my coach turning back into a pumpkin, it had me imagining that my eggs would shrivel up and die.

I had my first kid at 30, and I was anxious to have my second before that 35-year-old deadline. I was concerned that it would be more difficult to get pregnant after that and my pregnancy would be much riskier. I had a miscarriage at 32 and had a not-insignificant amount of stress about getting pregnant again as soon as possible. It would take about a year before I conceived, and I had my second child at 34 and precisely 4 months.

Considering how much stock I put in 35 as a marker, I was intrigued reading a new study from researchers at Harvard that suggests that women who are just over 35 may have slightly better pregnancy outcomes than women just under 35.

As Jessica Cohen, an associate professor of global health at Harvard’s T.H. Chan School of Public Health and a co-author of the study, told me, the choice of 35 as the cutoff for advanced maternal age was somewhat arbitrary in the first place. “Age 35 became a guideline in the ’70s for when to offer invasive genetic testing for Down syndrome,” she explained. After that, “age 35 became a guideline for a bunch of other things, and not really necessarily based on anything. Your risk of Down, your risk of stillbirth, pre-eclampsia — none of those change abruptly at 35,” she said.

Cohen noticed that she received subtly different treatment for the pregnancy she had before 35 and the one she had after that age. For example, during both her pregnancies, her blood pressure started creeping up above normal toward the end. When she was under 35, her health care providers just checked her blood pressure more regularly, but when she was over 35, she got an ultrasound, an amniotic fluid check and a nonstress test.

While Cohen noted that the American College of Obstetricians and Gynecologists does not explicitly say to do a certain set of tests once a woman is over 35, “the age influences what the provider recommends,” and it affects what kinds of testing insurance companies might pay for.

Because she’s an economist, Cohen said, she looks for natural experiments, and so with her colleagues she looked at over 50,000 pregnancies by using data from a large commercial insurer. About half of the women included in the study were 34.7 to 34.9 years old, and about half were 35.0 to 35.3 years old at the expected date of delivery.

The study found that women over 35 received more maternal-fetal medicine visits, more ultrasounds and more antepartum surveillance. There was also a 0.39 percentage point decline in perinatal mortality (defined in this study as a fetal death at or after 28 weeks’ gestation or an infant death up to a week postpartum). But the study found no significant difference in maternal mortality, preterm birth or low birth weight.

The takeaway isn’t that every pregnant person who’s just under 35 also needs more ultrasounds or more doctor visits, Cohen said. And it certainly isn’t that age doesn’t matter at all;