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A recent study published in Brain, Behavior, and Immunity provides evidence that higher levels of body fat during pregnancy are associated with an increase in systemic inflammation, which in turn predicts more attention-deficit/hyperactivity disorder symptoms in toddlers. The findings suggest that managing maternal inflammation during pregnancy could offer a pathway to support early child neurodevelopment.
Rates of overweight and obesity among women of childbearing age have risen steadily, raising questions about how increased body fat influences fetal development. Previous meta-analyses indicate that children born to mothers who are overweight or obese during pregnancy have a 30 to 60 percent relative increase in the likelihood of receiving an attention-deficit/hyperactivity disorder (ADHD) diagnosis compared to children of mothers with a healthy body composition.
Adipose tissue, commonly known as body fat, actively produces and secretes various immune molecules called cytokines. When body fat levels increase, this chemical signaling tends to trigger a state of persistent, low-grade systemic inflammation that is proportionate to the amount of excess adipose tissue.
During pregnancy, these inflammatory factors circulate in the mother’s blood and can influence the environment of the developing fetus. Elevated cytokines can alter placental function and amniotic fluid composition, which points to a potential biological pathway shaping fetal brain development in ways that increase liability for neurodevelopmental conditions. Animal models provide evidence that increased maternal inflammation affects offspring behavior, but human studies exploring this specific chain of events remain uncommon.
Elinor Sullivan, a professor in the departments of psychiatry and behavioral neuroscience at Oregon Health & Science University and director of the Prenatal Environment And Child Health lab, saw an opportunity to explore these early influences. “I have always been fascinated by the idea that brain development begins before a child is born,” Sullivan said. “We know that the prenatal environment plays a critical role in shaping lifelong health, yet we still understand relatively little about how factors such as maternal nutrition, metabolic health, stress, and mental health influence the developing brain.”
The research aimed to separate the effects of body fat from other common prenatal factors like diet and psychological stress. “What drew me to this work was the opportunity to identify modifiable factors during pregnancy that could improve children’s developmental trajectories,” Sullivan explained. “If we can better understand these early influences, we have the potential to design interventions that promote healthy brain development before symptoms of neurodevelopmental disorders ever emerge.”
The researchers sought to determine if gestational inflammation acts as a biological bridge linking maternal body fat to early signs of ADHD in human toddlers. Assessing behavior at two years of age captures a developmental period when self-regulation challenges first emerge and might be most receptive to supportive interventions. The study involved 297 pregnant women and their 302 children, a number that accounts for a few sibling pairs. During the second trimester, specifically between 24 and 26 weeks of gestation, the women visited a clinic to complete behavioral questionnaires and undergo biological assessments.
The research team measured maternal body fat percentage using air displacement plethysmography, a highly precise method that tracks whole-body density within a specialized enclosed chamber to determine the exact ratio of fat to lean tissue. The average body fat percentage in the sample, adjusted for pregnancy-related fluid changes, was 34 percent. To assess gestational inflammation, the authors collected fasting blood samples and analyzed the plasma for a comprehensive panel of cytokines, grouping the results into a single overarching inflammation score.
Dietitians conducted three unannounced dietary recalls, documenting everything the participants ate on two weekdays and one weekend day, to calculate a healthy eating index. Additionally, the women completed several standard questionnaires to measure symptoms of depression, anxiety, and perceived stress. When the children reached 24 months of age, the mothers rated 99 statements about their child’s behavior, with the researchers focusing specifically on the attention deficit and hyperactivity scale. The average score on the resulting ADHD symptom scale was approximately 3.1 out of a possible 10 points.
Throughout the analysis, the researchers controlled for several potential confounding variables. These included family income, maternal education, the mother’s own ADHD symptoms, her postnatal psychological distress, and observer ratings of her sensitive caregiving behaviors during a recorded play session.
When evaluating the data, the authors found that higher levels of maternal body fat during the second trimester were linked to increased maternal inflammation. Dietary quality and psychological distress did not show an association with gestational inflammation when considered alongside body fat. Maternal body fat emerged as the primary driver of the elevated inflammatory markers.
This finding ran counter to initial expectations about how different health behaviors interact during pregnancy. “I expected that obesity, nutrition, and stress during pregnancy would all be associated with inflammation,” Sullivan told PsyPost. “Instead, we found that maternal adiposity showed the strongest relationship.”
“That was surprising because it suggests these prenatal factors may not all influence fetal development in the same way, highlighting the need to better understand the unique biological pathways involved.” She added that future studies should examine if measures of nutrition and distress capture other aspects of maternal health separate from inflammation.
The analysis then evaluated the full pathway connecting the mother’s body fat to the child’s behavior. The data indicated that maternal body fat increased gestational inflammation, which in turn predicted higher ADHD symptom scores in the two-year-old children. The mediation model demonstrated an indirect effect, where body fat only influenced toddler behavior by first elevating the mother’s immune response. The direct link between maternal body fat and child ADHD symptoms was not statistically significant after accounting for inflammation, suggesting that the immune response mediates this relationship.
Independent of the inflammation pathway, the researchers also found that maternal psychological distress during pregnancy directly predicted greater toddler ADHD symptoms. This association held steady even after adjusting for the mother’s postnatal distress and observed parenting behaviors. The finding highlights that mental health during pregnancy exerts its own distinct influence on offspring behavior, separate from metabolic or dietary factors.
Summarizing the main results, Sullivan pointed out the utility of tracking these variables together. “This study suggests that inflammation during pregnancy may be one biological pathway linking maternal metabolic health to early childhood behaviors associated with attention-deficit/hyperactivity disorder,” Sullivan said. “Importantly, these associations were observed after accounting for several key factors, including maternal diet and psychological stress during pregnancy, which are rarely examined simultaneously in the same study.”
Elevated toddler ADHD symptoms do not guarantee a future clinical diagnosis, as behavioral regulation remains highly malleable at two years old. Early behavioral markers represent a potential window for support rather than a fixed developmental trajectory. In addition, the study relies on observational data, meaning the findings cannot establish that maternal body fat or inflammation directly causes changes in child behavior. Without controlled experiments, it remains unconfirmed whether reducing maternal body fat or inflammation would directly lower ADHD risk.
Sullivan emphasized that parents should interpret the findings as part of a much larger picture of child development. “It’s important that parents don’t come away thinking that maternal metabolic health determines whether their child will have ADHD,” Sullivan explained. “ADHD develops through a complex combination of genetic and environmental influences, and no single factor causes the condition. Our study suggests that inflammation during pregnancy may be one piece of that puzzle.”
She noted that viewing maternal health as a modifiable factor offers an encouraging message. “Our hope is to move beyond simply identifying risk factors and toward developing solutions,” Sullivan said. “We want to determine which aspects of maternal health during pregnancy can be safely improved and whether interventions like healthy nutrition, omega-3 fatty acids, and mindfulness can reduce inflammation and support healthy brain development.”
The method of grouping different immune molecules into a single inflammation score obscures biological differences between individual cytokines. Focusing on an aggregate score might hide how specific chemical pathways respond to diet or stress during pregnancy. Additionally, the participating families were predominantly non-Hispanic White and socioeconomically advantaged, with a median household income between $100,000 and $199,999. Environmental stressors and nutritional barriers in less advantaged or more diverse populations might alter the relationships between body weight, systemic inflammation, and child neurodevelopment.
Translating these biological findings into practical support will require a broad approach that looks beyond individual behavior. “One important message from this study is that improving maternal health is not solely the responsibility of individual women; it also requires supportive communities and public policies,” Sullivan said. She noted that individual strategies, such as adopting an anti-inflammatory diet or taking omega-3 supplements, should be complemented by efforts to create healthier environments.
Public infrastructure and accessibility play an essential role in maternal health during pregnancy. “Policies that improve access to affordable, nutritious foods, enhance neighborhood walkability, expand access to parks and recreational spaces, and support active lifestyles can make healthy choices more accessible for everyone,” Sullivan concluded. “Ultimately, improving maternal and child health requires both individual- and population-level approaches that support healthy pregnancies from the very beginning.”
The study, “The relationship between maternal adiposity during pregnancy and toddler ADHD symptoms is mediated by gestational inflammation,” was authored by Hanna C. Gustafsson, Geoffrey A. Dunn, Jennifer M. Loftis, Sarah L. Karalunas, Joel T. Nigg, and Elinor L. Sullivan.