Pregnancy-Related Risk Factors for Childhood Obesity
It is widely accepted that early childhood is a critical period that can set the trajectory of weight and metabolic health for the rest of a child’s lifetime – but a growing body of research is looking even further back in time for predictors of overweight and obesity. Studies examining prenatal and pre-pregnancy conditions as risk factors for overweight and obesity in offspring provide insight into the ways in which maternal health may impact infant health, and subsequently the health conditions of that infant later in life.
Maternal health conditions prior to pregnancy may already influence the health of her future children. A large meta-analysis found that higher maternal pre-pregnancy BMI was associated with higher risks of childhood overweight/obesity in early-, mid-, and late childhood, as shown in the figure below.
Source: Table adapted from Voerman et al., 2019
During pregnancy, maternal obesity is associated with a number of adverse outcomes for the fetus and newborn. It has been linked to macrosomia, which increases the risk of difficult labor and delivery, neonatal hypoglycemia, and obesity and metabolic syndrome later in life. Gestational diabetes mellitus is also commonly associated with neonatal hypoglycemia. Maternal obesity is associated with epigenetic effects on the offspring, indicating that these risk factors function at a molecular level. A large retrospective cohort study revealed that among low-income children, the relative risk of childhood obesity at 3 years of age was 2.3 times greater when the mother had obesity in the first trimester of pregnancy, compared to mothers whose weight was in the healthy range.
Maternal lifestyle practices during pregnancy have also been linked to the risk of offspring obesity. A large prospective cohort study found that at five years of follow-up, the incidence of obesity was lower among offspring whose mothers engaged in at least 150 minutes per week of moderate to vigorous physical activities, abstained from smoking, and consumed alcohol in moderation, compared with the rest of the cohort.
Many studies have examined the phenomenon of gestational weight gain as a determinant of offspring health. Gestational weight gain (GWG) is defined as “a change in maternal weights measured before pregnancy and prior to delivery.” GWG is crucial for the growth and development of the fetus, and both excessive and inadequate GWG can adversely affect maternal and infant outcomes. One study found that independent of parental BMI, mothers with greater GWG had children with increased skinfolds and BMI at 3 years of age. Excessive GWG was associated with a 32% greater risk of overweight compared to inadequate or adequate GWG. A healthful diet and greater physical activity during pregnancy are each associated with optimal GWG.
It is also important to note that the average age at which pregnancy occurs is young adulthood – an age group that accounts for 50% of adult obesity. The prevalence of obesity among young adults of age 18 through 25 years in the US has increased significantly over the past few decades. Young adulthood is a key period for preventing and treating obesity because of its important potential impact on the health of mothers and their children.
As we make progress in obesity research and treatment, the fundamental question of how we can prevent obesity in young adults remains. Successful prevention of obesity in parents could have a double benefit of preventing obesity in their children. Innovative approaches are essential to achieving this goal. For example, weight loss in parents that accompanies weight loss interventions in children could become an approved billable outcome by health plans.