"If you are healthy, over 40, and not obese, your risks of pregnancy complications are certainly less than an obese 40-year-old," says researcher John R. Barton, MD, director of maternal-fetal medicine at Central Baptist Hospital in Lexington, Ky. "And [they are] not that much different, other than a higher C-section rate, than a non-obese, younger woman."
He compared obese and non-obese pregnant women in his study. Some were in their 20s. Others were in their 40s.
Obese older women had more complications than older women at healthy weights, he found. Barton presented the findings this week at the annual meeting of the American College of Obstetricians and Gynecologists in San Diego.
While birth rates in younger women have been declining, pregnancy after 40 is on the rise, according to the CDC. From 2008 to 2009, the birth rate for women ages 40 to 44 increased by 3%, to 10.1 births per 1,000 women. That is the highest reported since 1967 for that age bracket.
Pregnancy After 40: Study Details
Barton looked at data on more than 53,000 women. They were enrolled in a pregnancy risk assessment and education program conducted by Alere, a health management and diagnosis company, between July 2006 and August 2011.
Of that total, 1,231 were 40 or older. Of those, 228 were obese.
A body mass index of 25-29.9 is considered overweight. A BMI of 30 or higher is considered obese.
Barton looked at four groups:
- Younger obese women, 20-29, with an average body mass index (BMI) of 35
- Older obese women, average age 41, with an average BMI of 35
- Younger non-obese women, 20-29, with an average BMI of 23
- Older non-obese women, average age 41, with an average BMI of nearly 24
- Older women, regardless of weight, were more likely to have C-sections. The obese older women were most likely. More than 69% of them had a C-section, while 55% of the older women at healthy weights did. Among the younger women, 47% of the obese and 28% of those at healthy weights had C-sections.
- Older obese women were most likely to deliver before 37 weeks. The early delivery increases the risk of health problems in the baby.
- Older obese women were three times as likely as older women at healthy weights to have gestational diabetes -- high blood sugar that develops during pregnancy. More than 21% of older obese women had it, compared to less than 7% of older women at healthy weights. Nearly 9% of younger obese women developed it, but less than 4% of younger, healthy-weight women did.
- Obese women in both age groups were more likely to get preeclampsia. In this condition, blood pressure rises and a high level of protein is found in the urine. It can be dangerous if untreated. It was about twice as common in obese women as in the women at healthy weights.
Pregnancy After 40: Perspective
Some of the differences are not surprising, says Suzanne Lubarsky, MD, a maternal-fetal medicine specialist at Kaiser Permanente Northwest in Portland, Ore. She reviewed the findings for WebMD.
"The diabetes part isn't surprising, because we know older women who are obese are going to have the highest rate," she tells WebMD.
The difference in the premature delivery rate was somewhat surprising, she says. "The C-section rate was somewhat surprising, although we know obesity is a risk factor for C-section."
The new data will provide much added support for advice that Lubarsky says she already gives to women 40-plus hoping to become pregnant. "Being at their ideal body weight [before pregnancy] optimizes their pregnancy and reduces their risks and the risks to their babies," she says.
Barton reports receiving research grants from Alere San Diego and Beckman Coulter Inc. Both grants are for the study of tests for preeclampsia.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.