Prenatal Exposure, Maternal Factors Drive Childhood BMI

Medscape

27-05-2025

Maternal factors, including high maternal prepregnancy body mass index (BMI), high weight gain during pregnancy, and smoking, were associated with an atypically high BMI trajectory in children, based on data from nearly 9500 children.
Childhood obesity remains a major risk factor for chronic health complications throughout life, and identifying modifiable early-life factors may help guide interventions and prevention, wrote Chang Liu, PhD, a psychologist at Washington State University, Pullman, Washington, and colleagues.
'This study allowed us to identify children following unhealthy growth trajectories as early as age 3.5 years and identify the point where BMI starts to show rapid changes such as adiposity rebound, creating crucial opportunities for intervention before obesity becomes established,' Liu said in an interview.
In a study published in JAMA Network Open , the researchers analyzed data from the Environmental Influences on Child Health Outcomes (ECHO) cohort from January 1997 to June 2024. The final study population included 9483 children (approximately half were boys) from 23 longitudinal pediatric cohorts in the United States and Puerto Rico born between 1997 and 2019.
The primary outcome was childhood BMI. The researchers categorized the children into two BMI trajectories, typical and atypical, using a novel model based on BMI shifts over time. Children with a typical trajectory (8477 children; 89.4%) showed linear BMI decreases to 6 years of age, followed by linear increases from age 6 to 9 years. Children with an atypical trajectory (10 children; 6%) showed early stable BMI from age 1 to 3.5 years, followed by rapid linear increases from 3.5 to 9 years.
The researchers assessed prenatal exposures to smoking, alcohol, and stress (depression or anxiety) as well as maternal characteristics of prepregnancy BMI, gestational weight gain, and child characteristics of preterm birth, birth weight, and breastfeeding.
The analysis used a multiphase latent growth mixture model to identify qualitative shifts in BMI during childhood that have not been addressed in previous studies, the researchers noted.
At 9 years of age, the atypical group had a mean BMI of 26.2, higher than the 99th percentile. Prenatal smoking, high prepregnancy BMI, high gestational weight gain, and high birth weight were significantly associated with the atypical trajectory.
The findings were limited by several factors, including the clinical utility of the researchers' multiphase model, which the researchers described as 'more computationally intensive than traditional methods of identifying abnormal childhood growth patterns.' Other limitations included the use of BMI values that may show variations in levels of adiposity based on age and sex, the lack of control for some social determinants of health, and incomplete data on BMI during school age and some perinatal exposures, the researchers wrote.
Implications and Research Gaps
Despite these limitations, the study identified factors that increase the risk for childhood obesity, and addressing these factors could help redirect unhealthy BMI trajectories, the researchers concluded.
'Without intervention, children exhibiting high BMI trajectories during childhood are more likely to develop overweight or obesity as adolescents and adults and are at higher risk for a range of metabolic and cardiovascular diseases throughout their lifetimes,' Liu told Medscape Medical News . Although examination of developmental pathways that lead to unhealthy vs healthy BMIs is crucial to identify modifiable early life factors, 'the challenge has been that most previous research couldn't pinpoint exactly when children's growth patterns start going off track,' Liu said.
Opportunities for clinicians include helping women of reproductive age achieve healthy weight and smoking cessation before pregnancy, supporting appropriate gestational weight gain during pregnancy, and closely monitoring children who show early signs of non-declining BMI patterns, especially those with identified risk factors, Liu said.
Further studies are needed to examine the biological mechanisms linking these early-life factors to different childhood BMI trajectories, Liu told Medscape Medical News . 'Additionally, research is needed to understand how social and environmental factors contribute to the racial and ethnic disparities we observed in growth patterns,' she said. 'Future work should test whether interventions targeting these modifiable factors during critical developmental periods can successfully help children maintain healthier growth trajectories,' Liu added.
Expanding Awareness of Obesity Risk
Early identification of risk for pediatric obesity can be crucial to minimizing disease morbidity and mortality, said Charles Hannum, MD, a general pediatrician at Tufts Medical Center, Boston, in an interview.
The current study not only confirms previously known risks but also adds new information to help pediatricians identify young children who would benefit from a more nuanced approach to growth monitoring and who may also benefit from a more robust prevention strategy for obesity, he said.
The data also show how maternal factors and the pregnancy environment influence child health, said Hannum. 'Lastly, this study is from a large, diverse population group, making the study conclusions more generalizable to the population of the United States,' he said.
Although some of the study findings were known, such as the association between childhood obesity and prenatal smoking, the current study adds the dimension of how that risk connects to the child's growth trend over time, said Hannum.
'The growth trend is often how pediatricians monitor this risk anecdotally,' he said. The associations between BMI trajectory and modifiable risks are not unexpected, but they help support the assumptions clinicians often make about obesity risk and can inform more focused and individually tailored prevention strategies, he noted.
The data can help support both public health initiatives and clinical practice at the individual level, Hannum told Medscape Medical News . For pediatricians, the findings support starting obesity prevention strategies early and monitoring children who have an at-risk BMI trajectory more frequently, he noted. When children do not follow a trajectory of decreased BMI from early to late toddlerhood, even if a BMI is normal, 'we now have evidence that they have an increased risk for developing obesity, and this knowledge may help to prevent some cases of pediatric obesity,' Hannum said.
Add More Variables in Further Research
The current study's limitations include missing and incomplete data and possible challenges when applying the trajectories to broad, diverse populations, given the complex contributors to pediatric obesity, Hannum told Medscape Medical News . More clarity is also needed on when and how to prioritize prevention strategies in the setting of additional obesity risk factors, Hannum added.