Expectant moms often justify an extra slice of cheesecake or late night pizza by saying they’re eating for two. But they might want to temper those indulgences. A new study published Tuesday in PLoS Medicine, says pregnant women who gain excessive amounts of weight contribute to their children becoming overweight.
“With the progression of the obesity [epidemic] there has been attention that over-nutrition could also have negative consequences,” says Dr. David Ludwig, director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital.
“It is quite extraordinary when you think about it; the effects during pregnancy can potentially have a lifetime implication.”
Ludwig looked at the body mass index (BMI) of 42,133 mothers at the birth of their 91,045 children and BMI data of these children until age 12. The researchers only studied mothers who had more than one child to rule out other confounding factors, such as genetics and environment. Siblings share the same genetics and generally grow up eating the same food and exercising the same. If one sibling was overweight but the other normal, researchers could rule out environment and genetics, something that has been difficult to do in other studies.
Then Ludwig compared the BMIs of each mother between her pregnancies to see if the mother's weight gain changed and if that influenced her child's weight.
“Variations in pregnancy weight gain accounted for a half unit difference in child BMI at an average of 12 years," Ludwig said. Since the 1970s when the obesity epidemic began, the change in BMI across the population increased by about two units. This effect remains small on an individual basis but could be one of the factors causing childhood obesity.
While researchers have long known that under-nutrition has a detrimental effect on children, this is the first study that shows that over-nutrition can also harm offspring.
“Excessive weight gain, above recommended levels, can also place that next generation at risk,” Ludwig says.
The study didn’t discuss just how much weight was too much to gain. It noted that weight gain recommendations vary—underweight mothers can gain the most, normal weight mothers can gain a little less, overweight mothers gain less, and obese mothers gain even less. Ludwig thinks that could change how moms think about maintaining a healthy weight for pregnancy.
This isn’t the only recent study to highlight the importance of a healthy weight during pregnancy. A paper published in JAMA found that women with a BMI of 35 to 40, within the range for obesity, were more likely to have extreme premature babies. Physicians recommend that women considering motherhood should think about weight loss or maintaining a healthy weight.
“Women are especially motivated during pregnancy because they are aware that the health of their baby is at stake,” Ludwig says. “Maintaining an optimal level of weight … is going to have ongoing benefits to your child.”