Women with large waistlines more likely to give birth to big babies

November 13, 2011 in Nutrition Topics in the News, Pregnancy and Breastfeeding

Women with large waistlines more likely to give birth to big babies

According to UK researchers, women who have large waistlines before pregnancy may be more likely to have a larger-than-normal newborn than women who are trim around the middle.

The findings concur with what experts know: women who are obese before pregnancy are more likely to have a baby with an abnormally high birth weight -- known as macrosomia (big baby).

By one definition, babies born weighing more than four kilograms (about eight pounds, 13 ounces) are macrosomic. Another definition puts the threshold at 4.5 kilograms, or nine pounds, 15 ounces.

Giving birth to a big baby can be difficult. Women may experience perineal tearing, blood loss or damage to their tailbone

In the study, researchers found that women with the biggest pre-pregnancy waistlines were more likely to have a macrosomic newborn, regardless of the definition.

Of nearly 3,100 women who gave birth over one year, about 10 percent had a baby weighing more than four kilograms and roughly one percent had newborns weighing more than 4.5 kilograms.

The risk was the highest among women who fell in the top 25 percent for pre-pregnancy waist-hip ratio. They were 57 percent more likely to have a baby weighing more than four kilograms, versus women in the bottom 25 percent for waist size.

They were also 2.6 times as likely to have a newborn weighing more than 4.5 kilograms.

It's known that total body fat is associated with pregnancy outcome. These new findings suggest that the distribution of a woman's body fat may also be important.

Studies have shown that having a large belly is more closely tied to the risks of diabetes and heart disease, versus excess body fat that is concentrated around the hips and thighs.

Currently, experts use BMI - not waist circumference - as the basis for weight-gain recommendations to pregnant women. The recommendations state that women who are obese (BMI of 30 or higher) should gain 11 to 20 pounds during pregnancy.

That's less than the 15 to 25 pounds recommended for overweight women (BMI between 25 and 30). Healthy weight women (a BMI between 18.5 and 25) are advised to gain 25 to 35 pounds. (To determine your BMI and waist-hip ratio, click here.)

If future studies point to the importance of waist size, weight-gain recommendations during pregnancy may need to be revised.

Experts recommend that women try to attain a healthy weight before becoming pregnant -- and they don't advise dieting to lose weight during pregnancy. Instead, the advice is to eat a balanced diet and get regular moderate exercise, like walking.

SOURCE: BJOG, online October 2011.

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