Maternal obesity may increase a child’s risk for attention-deficit hyperactivity disorder (ADHD), according to an analysis by researchers from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), part of the National Institutes of Health.
The researchers found that mothers–but not fathers–who were overweight or obese before pregnancy were more likely to report that their children had been diagnosed with attention-deficit hyperactivity disorder (ADHD) or to have symptoms of hyperactivity, inattentiveness or impulsiveness at ages 7 to 8 years old.
Their study appears in The Journal of Pediatrics.
The study team analyzed the NICHD Upstate KIDS Study, which recruited mothers of young infants and followed the children through age 8 years.
In this analysis of nearly 2,000 children, the study team found that women who were obese before pregnancy were approximately twice as likely to report that their child had ADHD or symptoms of hyperactivity, inattention or impulsiveness, compared to children of women of normal weight before pregnancy.
Women who were obese before pregnancy were approximately twice as likely to report that their child had ADHD or symptoms of hyperactivity, inattention or impulsiveness, compared to children of women of normal weight before pregnancy.
The authors suggest that, if their findings are confirmed by additional studies, healthcare providers may want to screen children of obese mothers for ADHD so that they could be offered earlier interventions.
The authors also note that healthcare providers could use evidence-based strategies to counsel women considering pregnancy on diet and lifestyle.
Resources for plus-size pregnant women and their healthcare providers are available as part of NICHD’s Pregnancy for Every Body initiative.
Globally, more than 10% of the population have a body mass index (BMI) in the obese range (BMI ≥ 30) with the prevalence having doubled in 70 countries in the past 25 years . In the United States, the age-adjusted prevalence is higher among women compared to men (40.1% vs. 35%) . And either at conception or during their pregnancy, 1 in 4 women have a BMI in the obese range .
Maternal obesity during pregnancy has critical health consequences for the mother, as well as acute and enduring metabolic consequences on the developing child . Recent studies further suggest that maternal obesity prior to or during pregnancy may also be related to cognitive and neurodevelopmental problems in offspring.
For instance, animal studies indicate that an obese state during pregnancy leads to a cascading series of events that affect brain development and subsequent neurodevelopmental functioning. Bilbo and Tsang (2010) showed in rats that gestational obesity produces changes in inflammatory signaling that has downstream effects on fetal microglial functioning, brain development and subsequent offspring spatial learning abilities .
In addition, obesity during pregnancy may also affect brain development via metabolic hormone-induced changes, such as exposure to increased circulating levels of leptin or insulin, or suppression of serotoninergic functions that disrupt the normal development of the serotonin (5HT) system .
It is also speculated that maternal dietary quality (e.g., high fat diet) may induce changes in fetal dopamine signaling and reward-related neural system development with consequences for offspring executive functions .
Studies of humans align with these findings from studies of animals. Maternal pre-pregnancy obesity has been linked with a number of cognitive and neurodevelopmental outcomes in offspring, such as cognitive/intellectual delay , poorer academic achievement scores , behavioral/emotional regulation problems  and an increased risk of Attention Deficit Hyperactivity Disorder (ADHD), Autism Spectrum Disorder (ASD) symptoms , and other developmental delays (DD) [12–14].
A recent meta-analysis of 32 studies found that relative to children born to normal weight mothers, children born to mothers who were obese during pregnancy were at greater risk for having a compromised cognitive or neurodevelopment outcome (OR = 1.51). Within this body of literature, ADHD and related symptoms was the least investigated outcome (n = 7 in meta-analysis), but had the highest odds ratio (1.62) associated with pre-pregnancy obesity .
Of note, however, studies have also documented null associations between pre-pregnancy weight and neurodevelopmental outcomes [16,17], and discordant sibling design studies suggested that the association may not be causal [18,19].
Given some of the differences in findings, continued research is needed using different samples and different methods to better understand this association between pre-pregnancy obesity and child neurodevelopmental outcomes.
Understanding prenatal and developmental factors associated with ADHD and poor executive self-regulation is important since childhood symptoms in these domains, independent of a clinical diagnosis, can increase the risk for a number of unhealthy behaviors later in adulthood [20,21] and has a large economic burden [22–24].
Thus, to better inform antenatal prevention and postnatal risk-identification/remediation strategies, continued research is needed to further clarify early risk factors for ADHD symptoms and poor executive self-regulation, including the extent to which pre-pregnancy obesity is related to childhood ADHD symptoms and related behaviors.
The purpose of this study was to add additional data to this growing body of literature. First, this study includes assessment of both ADHD symptoms and behaviors in everyday life that depend on executive self-regulation processes (e.g., those that involve negotiation of competing desired outcomes).
Second, whereas existing studies have focused primarily on school age children, the study population herein is a sample of preschool age children. If associations are present at the preschool age, it may provide further justification for earlier monitoring of behavioral problems among children born to mothers obese prior to and during pregnancy.
Third, we examined both continuous and categorical indicators of pre-pregnancy BMI and gestational weight gain (GWG) in order to identify associations at varying levels of exposure. In addition, we used inverse probability weighting (IPW), a robust method for accounting for sample selection bias and confounding in observational studies [25,26].
In light of existing research, we hypothesize that children born to mothers with higher pre-pregnancy BMIs or greater GWG will display greater ADHD symptoms and poorer executive self-regulation behaviors.
. Conclusions This study supports a growing body of literature both from animal and human studies that find offspring born of mothers with excess weight prior to or during pregnancy are at increased risk for cognitive and neurodevelopmental problems, including more ADHD and related executive self-regulation problems. Notably, the effect sizes observed here were small.
For example, the standardized beta for pre-pregnancy BMI ≥ 35 and ADHD symptoms was 0.21. Small or medium effect sizes would be expected in studies of outcomes, such as ADHD symptoms or executive functioning behaviors, where there are likely multiple causal pathways.
To put the effect we observed in perspective, the Cohen’s d effect size for maternal smoking during pregnancy and ADHD is ~0.48 (based on a pooled OR of 2.36 from a meta-analysis) . However, the prevalence of maternal smoking during pregnancy is around 7% , whereas the prevalence of pre-pregnancy obesity is approximately 25%, with greater increasing trends being observed among women with more severe obesity (BMIs ≥ 35) .
Thus, given the current prevalence of obesity, the small effect size observed here may have an equally, if not greater, impact at the population level relative to other risk factors that are less frequent, but have a larger effect size.
Understanding factors that contribute to early childhood self-regulation problems, such as hyperactive-impulsive symptoms and problems related to attention and poor executive control is important since deficits in these areas can alter the trajectory of health and have a profound impact on their economic burden to society.
For instance, Caspi, et al. (2016)  recently showed that variation in age-three “brain health” (a global index of early cognitive abilities and examiner rated self-regulation behaviors) significantly predicted individuals who as adults would be members of the population with a constellation of economically burdensome health outcomes (excess obesity, higher prevalence of smoking, greater hospital utilization, etc.).
On an individual level, maintaining a healthy periconceptional and pregnancy weight is warranted for the overall health benefits to the woman and her fetus, but clinical action to specifically reduce ADHD in the offspring born to these women is not warranted at this time.
Nevertheless, if studies continue to show similar results as shown here, periconception, prenatal and postnatal risk-identification/remediation education and communication strategies could be leveraged to help foster optimal “brain health” and lower the risk of ADHD and related executive self-regulation among pregnant women with high levels of obesity.
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