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Maternal obesity risk

Maternal obesity increases risk for major birth defects

Among the offspring of mothers of normal weight, as well as underweight ones, the rate of congenital malformation was about 3.4 percent

Children of obese women are more likely to be afflicted by major birth defects, including malformations of the heart and genitals, according to a study by researchers from Sweden. For the study, researchers used data on more than 1.2 million births registered in Sweden from 2001 to 2014. They gathered information on major congenital malformations and compared this to the BMI of the mother at the time she gave birth.

"We found that risks of major congenital malformations in offspring progressively increase with maternal overweight and severity of obesity," researchers note. "Thus, efforts should be made to encourage women of reproductive age to adopt a healthy lifestyle and to obtain a normal body weight before conception."

The paper, ‘Risk of major congenital malformations in relation to maternal overweight and obesity severity: cohort study of 1.2 million singletons’, was published in The BMJ.

They found that just over 43,500 of the children studied had a major malformation, the researchers found. The most common was a heart defect, followed by malformation of the genital organs, the limbs, the urinary system, the eye, digestive system, facial clefts and nervous system defects of the spine or brain.

Compared with offspring of normal weight mothers (risk of malformations 3.4%), the proportions and adjusted risk ratios of any major congenital malformation among the offspring of mothers with higher BMI were: overweight, 3.5% and 1.05 (95% confidence interval 1.02 to 1.07); obesity class I, 3.8% and 1.12 (1.08 to 1.15), obesity class II, 4.2% and 1.23 (1.17 to 1.30), and obesity class III, 4.7% and 1.37 (1.26 to 1.49).

The risks of congenital heart defects, malformations of the nervous system, and limb defects also progressively increased with BMI from overweight to obesity class III. The largest organ specific relative risks related to maternal overweight and increasing obesity were observed for malformations of the nervous system. Malformations of the genital and digestive systems were also increased in offspring of obese mothers.

Among the offspring of mothers of normal weight, as well as underweight ones, the rate of congenital malformation was about 3.4 percent, the researchers found.

This rose to 3.5 percent for children of overweight women, 3.8 percent for obese ones, 4.2 percent in the severely obese category and 4.7 percent for the morbidly obese. The risk was higher for boys than for girls.

The study took into account other potential risk factors such as maternal smoking or drinking, socio-economic status, diabetes, the use anti-epileptic drugs, and vitamin deficiency.

“We found that risks of major congenital malformations in offspring progressively increase with maternal overweight and severity of obesity. This underlines the importance of having a maternal BMI in the normal range before pregnancy,” the researchers conclude. “Preventive effects of weight reduction in early pregnancy cannot be expected as organogenesis occurs within the first eight weeks of gestation. Thus, efforts should be made to encourage women of reproductive age to adopt a healthy lifestyle and to obtain a normal body weight before conception.”

To view this paper, please click here

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