It’s well established more people are having babies later in life than at any other time in U.S. history.
This increase in the number of people giving birth after the age of 35 – designated as “advanced maternal age” in clinical obstetrics – started in the mid-1970s and hascontinued to climb, according to the Centers for Disease Control and Prevention.
A federal report shows 18% of pregnancies were in people 35 and older in 2018, up from 15% in 2013 and 11% in 2002 and 8% in 1990.
The American College of Obstetricians and Gynecologists says pregnant people in this age group are at higher risk of gestational diabetes and high blood pressure. They’re also more likely to have a low birth weight baby and premature birth, and need a C-section.
Despite these risks, a study published Friday in JAMA Health Forum shows patients just over the age of 35 had better prenatal care and pregnancy outcomes compared to those who were a few months shy of the cutoff age.
“There’s so many of these arbitrary guidelines and cutoffs in medicine," said study senior author Jessica Cohen, an associate professor at the Harvard T.H. Chan. School of Public Health. "The label of ‘advanced maternal age’ makes you feel really old when you’re just 35.”
Cohen's personal experience inspired the study. She had her first child at 34, and while she said she received amazing care, there was a difference during her second pregnancy at 36.
“When I had the second and I noticed how carefully I was being watched, I was like, ‘Wow, I wish I had this the first time,’” Cohen said.
The authors studied more than 50,000 deliveries from 2008 to 2019. About half of the people giving birth were between 34.7 and 34.9 years old, and the other half were between 35 and 35.3.
Prenatal care including ultrasounds, visits with maternal-fetal medicine specialists and special monitoring of the fetus all increased in those over 35 years old. Authors also found stillbirths and early newborn deaths dropped.
“Definitely, for sure, risks increase with the mom’s age,” Cohen said. “But there’s no risk that jumps right as you become age 35."
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After controlling for underlying conditions like pre-gestational diabetes, chronic hypertension and obesity, researchers found a stronger association between older age, more prenatal care services, and lower perinatal mortality.
Prenatal services may partially affect stillbirth and infant mortality rates after birth, but the study left out key information that impacts pregnancy outcome, said Dr. Priya Rajan, associate professor of maternal fetal medicine at Northwestern University Feinberg School of Medicine and chief of diagnostic ultrasound at Northwestern Medicine.
“Timing of delivery and the number of pregnancies you had play a big part of it, too,” she said. “They tried to control a little bit for the ethnic variation and race data, but not to have any of that is really limiting.”
Additionally, the study’s data came from a large, nationwide commercial insurer so didn't include people on Medicaid or Medicare or those with no insurance at all, Rajan said.
The study also showed increased prenatal care didn't appear to reduce maternal deaths among pregnant patients over 35.
“That’s something that we really want to make sure we’re paying attention to,” Rajan said.
Despite its limitations, she said the study raises awareness for people of advanced maternal age and the care they receive during pregnancy. More data is needed to understand what aspects of prenatal care are making the biggest difference among pregnant people with traditional risk factors.
“We really need to rethink how we’re taking care of pregnant women,” Rajan said. “All pregnant people – regardless of age, regardless of race, regardless of socioeconomic status – we need to universally improve care.”
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