How Does A Pregnant Woman’s Weight Influence Her Child’s Infection Risk?

By Dennis Thompson HealthDay Reporter

WEDNESDAY, June 4, 2025 (HealthDay News) — Children born to women who are obese have a higher risk of landing in a hospital with a severe infection, a new study says.

Infants under 1 year of age have a 41% increased risk of hospitalization for infection if their mom was severely obese during pregnancy, researchers reported June 3 in the journal BMJ Medicine.

And that risk extends into childhood and adolescence, with 5- to 15-year-olds 53% more likely to require hospital treatment for an infection, the study found.

“Most excess hospital admissions for infection were caused by respiratory and gastrointestinal infections, and multisystem viral infections,” wrote a team led by Victoria Coathup, a researcher in epidemiology with the University of Oxford in the U.K.

“The findings indicate a need to help women achieve and maintain a healthy weight before conception,” researchers added.

The percentage of women who are obese while pregnant has nearly doubled, rising to more than 16% in the 2010s from under 9% in the 1990s, researchers said in background notes.

To explore the potential health risks to children of obesity during pregnancy, researchers turned to a long-range study of 9,540 births in Bradford, U.K., between March 2007 and December 2010.

About 56% of the mothers were overweight or obese during pregnancy, researchers found.

Expectant moms with severe obesity — a body mass index (BMI) of 35 or higher — wound up with kids who had an increased risk of infection, results show. (BMI is an estimate of body fat based on height and weight.)

Surprisingly, one common risk factor of obesity during pregnancy — pre-term birth — had little to do with this risk, accounting for only 7% of the link between maternal obesity and childhood infections.

C-section birth accounted for 21% of the risk, and childhood obesity by ages 4 to 5 accounted for 26%, researchers found. Addressing either of these might reduce kids’ infection risk.

Researchers speculate that obesity during pregnancy might influence kids’ inflammatory processes, genetics, metabolism and gut biome, any of which “could influence the developing immune system, thus contributing to increased vulnerability to infections during childhood.”

Doctors should encourage women of childbearing age to reach and maintain a healthy body weight, researchers concluded.

“Pregnancy has been identified as a teachable moment for potential sustainable lifestyle changes,” researchers wrote. “Therefore, supporting women during pregnancy and the postnatal period to change unhealthy diet and lifestyle choices might positively influence the health of women as well as the body mass index of their offspring.”

More information

The American College of Obstetricians and Gynecologists has more on obesity and pregnancy.

SOURCES: BMJ, news release, June 2, 2025, BMJ Medicine, June 3, 2025

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