Maternal weight gain that meets or exceeds recommendations made in current guidelines is associated with a fourfold increased risk of having a baby that is overweight in childhood, results of a large prospective study suggest.
Compared with women who had inadequate weight gain as defined by current Institute of Medicine (IOM) guidelines, those who had adequate or excessive gain were at increased risk of having an overweight child (odds ratios of 3.8 and 4.3, respectively).
The current societal trend of more overweight mothers and children is outpacing the IOM's guidelines for gestational weight gain, published in 1990. Since then, “excessive gains have become more common,” wrote study investigators Dr. Emily Oken and her colleagues at the department of ambulatory care and prevention, Harvard Medical School, Boston.
The researchers therefore recommended that the guidelines be updated to better reflect today's mothers and children.
The study—which was published in the American Journal of Obstetrics and Gynecology—is one of a few that have examined the links between weight gain during pregnancy and child weight outcomes after birth, according to the researchers. Most studies, they wrote, “have not considered gestational weight gain when predicting obesity perinatally.”
According to the IOM's standards, women with a normal prepregnancy body mass index (19.8–26.0 kg/m
The researchers recruited their participants through Project Viva, a prospective cohort study of pregnant women and their children. Of the 2,128 women who delivered a live singleton infant in that study, Dr. Oken and her colleagues examined 1,044 mother/child pairs.
Gestational weight gain was calculated as the difference between the last weight recorded before delivery and self-reported prepregnancy weight (Am. J. Obstet. Gynecol. 2007;196:322.e1–8).
The mean maternal prepregnancy BMI was 24.6 kg/m
According to the IOM's standards, 51% of these women gained excessive weight, 35% gained adequate weight, and 14% gained inadequate weight.
Although the researchers recorded a number of factors including age, income, education, and time between the last pregnancy weight and delivery, they did not include these factors in their final models because adjusting for them did not “appreciably change estimates.”
At the time of the analysis, the researchers reported that all the children completed the study visit at age 3 years.
The researchers found the mean child BMI z score was 0.45 units. Nine percent of children were overweight, defined as a BMI of equal to or greater than the 95th percentile. “Children of mothers in all Institute of Medicine weight gain groups, even those with inadequate gain, had mean BMI z scores above the median of the 2000 CDC growth curves, which were primarily based upon U.S. children in the 1970s,” they wrote. On bivariate analysis, investigators found “gestational weight gain was directly associated with child overweight (odds ratio 1.3).”
Dr. Oken and her colleagues reported that children of mothers who gained more weight also had somewhat higher systolic blood pressure. Even mothers with “adequate gain” still had a substantially higher risk of having children who were overweight. They also warned that “higher gestational weight gain may cause undesirable birth outcomes such as increased rates of macrosomia and cesarean sections and is associated with higher postpartum weight retention and later risk for obesity in the mother.”