Determining the interplay of prenatal parental BMI in shaping child BMI trajectories: the CHILD Cohort Study.

Background: Obesity is a major public health concern affecting millions of people globally. Early identification of individuals susceptible to obesity is crucial for reducing the burden of obesity. Obesity is often defined based on body-mass-index (BMI), and tracking BMI trajectories from early childhood offers a valuable tool for risk stratification. Although the role of mothers in shaping these trajectories is well-recognized, the paternal influence on childhood obesity development remains a knowledge gap. We hypothesize that children of fathers with obesity have higher odds of being in the rapid BMI growth trajectory with stronger estimates when the mother is also with overweight or obesity.

Methods: We analyzed data from the Canadian CHILD Cohort Study, a pregnancy cohort in which both parents were enrolled in early pregnancy when BMI was assessed. The child's BMI was repeatedly collected from birth to age five. We used group-based trajectory modeling to identify offspring BMI z-score (BMIz) trajectory groups (age-and-sex standardized) and weighted multinomial logistic regression analysis to determine the associations between prenatal paternal BMI and offspring growth trajectories, stratified by maternal weight categories.

Results: Among 2 238 participants, the mean prenatal paternal BMI was 27.44 (SD = 4.77), and 22.83% of fathers were with obesity. The four identified offspring BMIz trajectories were: low stable (n = 220, 9.83%), normative (n = 1 356, 60.59%), high stable (n = 572, 25.56%), and rapid BMIz growth trajectory (n = 90, 4.02%). Children of normal-weight mothers and fathers with obesity had 1.86 higher odds (OR: 1.86; 95%CI: 1.22-2.84) of being classified in the rapid growth BMIz trajectory, compared to children of normal-weight fathers. The odds of being in the rapid growth BMIz trajectory were higher when both mothers and fathers were with obesity (OR: 4.35; 95%CI: 2.65-7.14).

Conclusions: Children of fathers with obesity had higher odds of being in the rapid BMI growth trajectory, particularly when also the mother was with overweight or obesity. These results support the need for preconception advice and interventions for couples to optimize their offspring's health.