Inter-generational link of obesity risk: role of the placenta
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OBJECTIVE: High prepregnancy maternal body mass index (BMI) is associated with an increased risk in childhood overweight and obesity. This study sought to expand upon the research of this phenomenon/trend by examining the role of placental weight in inter-generational obesity risk. METHODS: This prospective birth cohort study was conducted at Boston Medical Center in Boston, Massachusetts. Between 1998 and 2016, the study recruited and tracked 1,025 mother-infant pairs who have been followed from birth prospectively up to age 19 and who had data on placental pathology along with pre-, peri-, and post-natal variables, including maternal and child BMI. This study analyzed 6 Groups defined by placental weight tertiles and maternal overweight and obesity (BMI ≥ 25 kg/m2) (binary). Group 0 includes lowest placental tertile and maternal not overweight and obesity. Group 1 includes lowest placental tertile and maternal overweight and obesity. Group 2 includes middle placental tertile and maternal not overweight. Group 3 includes middle placental tertile and maternal overweight and obesity. Group 4 includes highest placental tertile and maternal not overweight. Group 5 includes highest placental tertile and maternal overweight and obesity. MAIN OUTCOMES AND MEASURES: Child BMI z-score was calculated according to United States reference data for specific age and sex. Childhood overweight and obesity was defined as an BMI in the 85th percentile or greater for age and sex. Maternal overweight and obesity was defined as a BMI of 25kg/m2 or greater, and placental weight was classified into tertiles based on sex- and gestational age. RESULTS: The mean (SD) maternal age at delivery was 28.7 (6.6) years and the mean (SD) child age at last visit was 9.5 (4.9) years. Among 1,025 mothers, 54.15% were overweight with an average BMI of 27.0 kg/m2. 68.98% of mothers were black, 76.5% never smoked, and 62.73% had less than a high school education. Among 1,025 children 447 (43.61%) were overweight. As expected, maternal overweight and obesity was associated with the highest risk for childhood overweight and obesity, with an odds ratio of 3.752 (95% CI, 2.137-6.588) as well as the largest increase in child BMI z-score. The strong association remained after adjusting for placental weight and other covariables, including birth weight. When maternal overweight and obesity and placental weight were analyzed in combined groups (0-5), they jointly increased the risk of child overweight or obesity. Using group 0 as reference, the group 5 had the highest risk of child overweight or obese and the largest increase in child BMI z-score. CONCLUSIONS: In this urban low-income prospective birth cohort, we observed a strong inter-generational link of overweight or obesity. Furthermore, there was an additive effect of maternal overweight and obesity and placental weight on child risk of overweight and obesity. Additional studies are warranted to replicate our findings and further investigate the biological pathways underlying the inter-generational obesity risk.