The interactive effect of pre-pregnancy overweight and obesity and hypertensive disorders of pregnancy on the weight status in infancy

We aimed to assess whether hypertensive disorders of pregnancy (HDP) could modify the effect of pre-pregnancy overweight or obesity (OWO) on the risk of offspring high body mass index (BMI) in infancy. A total of 3,765 mother-child pairs were recruited from two Chinese birth cohorts. BMI ≥ 85(th) percentile, based on World Health Organization criteria, was defined as a high BMI for the risk of developing severe obesity in later life. Logistic regression analysis was used to assess the combined effects and multiplicative interactions of pre-pregnancy OWO + HDP on offspring high BMI. Relative excess risk due to interaction (RERI) or attributable proportion (AP) was used to estimate additive interactions. RERI > 0 or AP > 0 indicates a significant additive interaction. Compared with the non-OWO and normal blood pressure group, the combination of OWO + HDP was positively associated with offspring high BMI at 12 months of age [OR 3.10 (95%CI 1.59, 6.04)], with 51% of the effects attributed to an additive interaction [AP 0.51 (95%CI 0.13, 0.89)]. An interactive effect was found between the pre-pregnancy OWO + HDP and offspring high BMI in infancy. Interventions to control pre-pregnancy OWO and HDP are important to prevent obesity and associated adverse outcomes in offspring.