Published: Oct 1, 2013 |

Increases in a mother’s weight during pregnancy were associated with elevated body mass index (BMI) and odds of overweight and obesity in her child through age 12, researchers found.

Among a cohort of women who had two or more pregnancies, each kg of weight gained during pregnancy was significantly associated with a 0.0220 increase in the child’s BMI (95% CI 0.0134-0.0306,P<0.0001) at around 12 years, according toDavid Ludwig, MD, PhD, of Boston Children’s Hospital, and colleagues.

Additionally, every kg gained during pregnancy was associated with significant increased odds of the child being overweight or obesity (odds ratio 1.007, 95% CI 1.003-1.012, P=0.0008), they wrote online in the October 1 issue ofPLoS Medicine.

Mothers’ weight and weight gain during pregnancy have been tied to a number of health effects in their children. Obesity in pregnant mothers has been associated with earlier death and risk for hospital admission due to cardiac events in the child.

Rapid weight gain in pregnant mothers has been tied to elevated risks for gestational diabetes.

The authors analyzed the relationship between maternal weight gain during pregnancy with the child’s weight at an average age of 11.9 in a population-based cohort of 42,133 Arkansas women and 91,045 of their children. The women had more than one singleton pregnancy.

Birth data included pregnancy weight gain, birth weight of the baby, diabetes during pregnancy, week of gestation at delivery, maternal age, maternal education, maternal marital status, maternal smoking, child sex, child parity, and year of birth, which were collected through the Vital Statistics Natality records.

Weight gain was determined by subtracting reported prepregnancy weight from weight at delivery.

Children’s weight and height at a mean 11.9 years were recorded through school records and were used to calculate BMI.

Data were collected on all live births in Arkansas from January 1989 to December 2005, and children were followed-up with from August 2003 to June 2011.

At birth, mothers gained a mean 13.9 kg from their prepregnancy weight. Their mean age was 24.6 and 17.9% smoked.

Children had a mean birth weight of 3,416.5 g, a mean gestation of 39.3 weeks, and 39.4% were overweight or obese at the time of their last BMI measurement.

Birth order had no significant effect on maternal weight gain during pregnancy, child’s birth weight, BMI at last measurement, or age of BMI measurement.

Although each kg the mother gained during pregnancy was associated with increases in childhood BMI and in odds of overweight or obesity, the associations with BMI were “modestly attenuated” after adjustment for birth weight by roughly 35%. After adjustment, each kg of maternal weight gained during pregnancy was associated with a childhood BMI increase of 0.0143 kg/m² (95% CI 0.0057-0.0229, P=0.0007).

The authors concluded that “because childhood body weight predicts adult body weight, our study suggests that overnutrition in pregnancy may program the fetus for an increased lifetime risk for obesity, though the magnitude of this effect may be small.”

“However, because inadequate weight gain during pregnancy can also adversely affect the developing fetus, it will be essential for women to receive clear information about what constitutes optimal weight gain during pregnancy,” they added.

They cautioned that the study was limited by missing data for prepregnancy BMI, potential errors in reporting pregnancy weight gain, and lack of paternal data.

Ludwig and colleagues also could not account for biological or behavioral factors that may affect their findings, such as diet, physical activity, and other maternal characteristics.