PITTSBURGH (KDKA) — Abby Parkes needed a caesarean section to deliver her son, Lucas.

It was a decision she did not take lightly.

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“It was for health reasons, really. If I had a choice, I would have had a natural birth,” she says.

“There are obvious, very important medical reasons why women choose to do C-sections, whether it be emergent or planned, but there are also other women who make decisions to have a C-section that are not necessarily medically necessary,” says Allegheny General Hospital med-peds physician Dr. Jennifer Preiss.

Now, new research from Imperial College London shows C-section babies could have weight issues later on.

“There is an association between being born by C-section and increase of odds of overweight and obesity as adult,” says Professor Nenna Modi, of the Imperial College London.

The study of 150,000 births found C-section babies are 25 percent more likely to be heavier as adults.

“I hadn’t really paid much attention to it until I saw this study,” Dr. Preiss admits. “But I think overall, I would probably agree with the study that the children who have been born by C-section probably are overweight.”

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Study author Neena Modi says the findings suggest not having a natural birth may affect a baby’s metabolism.

“We need to be exposed to bacteria that comes from mother that a baby may not be exposed to if it is born by C-section,” she says.

“Women who are making some decisions about how they’re going to deliver their baby need to be much more aware that elective c-sections are not without some risk to their child, and we’re not talking perinatal period or neonatal period, but long term,” adds Dr. Preiss.

About a third of all babies in the U.S. are born by C-section. Previous research has shown C-section babies may be at higher risk for asthma and childhood diabetes.

“It would be really nice if we could get a group of women who choose to have a C-section that is elective, and then sort of do a study and look at what happens long-term to their children,” says Dr. Preiss.

Abby is not concerned at this point.

“My little boy is particularly healthy. He is long and thin, so it doesn’t worry me,” she said.

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Other factors may also play a role in C-section babies gaining weight later on, including maternal weight, age and lifestyle.