What You Gain Won't Affect Baby's Brain

Pregnancy weight gain does not share a link with children's cognitive performance

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Although gaining too much or too little weight during pregnancy can cause problems for the baby, cognitive problems are not among them.

A recent study looking at the relationship between how much weight an expectant mother gains and her child's cognitive performance, researchers were able to gather enough data to take into account a wide range of factors that might have influenced past studies.

"Talk to your OB about appropriate weight gain during pregnancy."

"One challenge for studies examining gestational weight gain and child outcomes is separating the effect of gestational weight gain from confounders," said lead author Sarah Keim, Ph.D., from the Center for Biobehavioral Health at The Research Institute at Nationwide Children's Hospital in Columbus, Ohio.

"Confounders such as maternal intelligence, whether the family environment promotes cognitive development, family diet and exercise and some genetic factors can influence neurodevelopment postnatal and also gestational weight gain," she said.

But the study Keim and her colleagues conducted was able to account for these factors in looking at women's weight gain during pregnancy and their children's brain power at age 4 and age 7.

Keim's study calculated associations with pregnant women's characteristics based on data from the U.S. Collaborative Perinatal Project, which ran from 1959 to 1973. The researchers included in their analysis women who had single children at term. A total of 31,968 children were evaluated at 4 and 7 years using standard intelligence scales.

First, the researchers used traditional statistical methods to control for the mother's weight before pregnancy, her race and the gender of the baby. Then they used a different method to control for a range of other possible "confounding" factors that siblings might share, such as certain genetic factors and parenting methods.

They concluded from their analyses of the data that gaining too much or too little weight did not by itself cause any problems with children's cognitive performance. Any apparent associations that were seen ended up vanishing when the genetic or family characteristics were considered.

Among the characteristics they included in their calculations were the mother's age, race, socio-economic status, smoking status and insurance status.

Keim said, however, that this study could not take into account every possible other confounding factor - simply much more than what previous studies had done. This study focused only on babies born on time (not preterm), she said.

"Our findings suggest that gestational weight gain is generally unassociated with child cognitive development," she said.

According to the Institute of Medicine gestational weight gain guidelines, the amount of weight a woman should gain during pregnancy depends on her body mass index (BMI) before she gets pregnant.

If she is underweight, with a BMI less than 18.5, she should gain 28 to 40 pounds, or about a pound a week in the second and third trimesters. Women with a "normal" BMI between 18.5 and 25 should gain between 25 and 35 pounds during pregnancy at the same rate of a pound a week after the first trimester.

Women considered overweight, with a BMI between 25 and 30, should gain 15 to 25 pounds during their pregnancy, and obese women, with a BMI over 30, should gain only 11 to 20 pounds.

Women who gain more than the recommended amount may give birth early or see obesity or behavioral problems in their children. Those who don't gain enough may also give birth prematurely or have children who die or have a low birth weight.

The study appeared online ahead of print in February in the International Journal of Epidemiology. It was funded internally by the hospital, and the authors declared no conflicts of interest.

Reviewed by: 
Review Date: 
March 1, 2012
Last Updated:
March 1, 2012