Objectives: to estimate the role of maternal overweight and obesity before pregnancy as predictors of childhood asthma in a population of Peruvian children under five years. Methods: we carried out a retrospective cohort study of children aged five years or less and their mothers from the Regional Hospital of Ayacucho and the María Auxiliadora Hospital in Lima, Peru. We included children who were born between 2013 and 2014 and follow them up until 2018 and 2019, respectively. The diagnosis of overweight and obesity of the mother before pregnancy and asthma in the child were registered in their clinical histories. Crude (cRR) and adjusted relative risks (aRR) and 95% confidence intervals (CI95%) were obtained using a generalized linear model of the Poisson family with link log and robust variances. Results: We evaluated 431 medical records and found that 20.9% of the children had asthma,...