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Obesity Increases Birth Defect Risk

Heart, Spine, and Limb Defects Seen More
By
WebMD Health News
Reviewed by Louise Chang, MD

Aug. 6, 2007 -- Babies born to mothers who are obese prior to and during pregnancy are at increased risk for a range of major birth defects, new research shows.

Pre-pregnancy obesity has previously been linked to an increase in birth defects involving the brain and spinal cord. This association was seen in the new study, and researchers also reported an increase in heart, limb, and gastrointestinal birth defects among babies born to obese moms.

Obese women were at increased risk for delivering babies with seven of 16 major birth defects evaluated by the researchers.

But researcher D. Kim Waller, PhD, of the University of Texas School of Public Health, tells WebMD that the chance of delivering a child with a major birth defect is still low for obese moms.

According to Waller, based on the study’s findings, major birth defects could be expected in four out of 100 babies born to obese mothers. The average birth defect risk is closer to three in 100 births among babies born to normal-weight mothers, he notes.

"Obese women should not be overly alarmed by these findings, but it is important to understand the risk," she says. "While the absolute risk that an obese woman will have an infant with a birth defect is low, the contribution to the public health, given high rates of obesity in the U.S., is significant."

Twofold Rise in Spina Bifida

Interviews were conducted with 10,249 women in eight states who gave birth to babies with birth defects between 1997 and 2002 and with 4,065 women who delivered babies without birth defects during the same period.

The birth defect found to be most strongly linked to obesity in the study was the neural tube defect spina bifida.

Compared with babies born to normal-weight women, babies born to obese women in the study were twice as likely to have the neural tube defect even though obese moms were just as likely to take folic acid supplements prior to conceiving.

Taking folic acid before pregnancy dramatically reduces the risk of spina bifida and related neural tube birth defects.

A slightly lower increase in risk was identified for omphaleocele, a condition in which the intestines or another abdominal organ protrudes through the navel.

Obesity-related risk increases in the range of 20% to 50% were also seen for heart defects, limb abnormalities, malformations in the anal opening or urethra in boys, and a condition known as diaphragmatic hernia, which can interfere with lung development.

The study is published in the August issue of the Archives of Pediatric and Adolescent Medicine.

Diabetes and Birth Defects

Having uncontrolled or poorly controlled diabetes prior to conception or early in pregnancy has been linked to an increased risk for major birth defects in both animal and human studies.

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