Abstract: Objectives: We examined if the guidelines for gestational weight gain (GWG) proposed by the Institute of Medicine (IOM) are the most suitable for Chilean women. Study design: Secondary analysis of records of single full-term births at the Dr. Sotero del Rio Hospital, Santiago, Chile, during 2003-2012 (n = 62,579). Methods: From clinical records, we obtained data regarding maternal age, height, prepregnancy and at delivery weights, pathologies during pregnancy such as gestational diabetes (GDM) and pre-eclampsia, gestational age at delivery, and number of infants born small for gestational age (SGA) and large for gestational age (LGA). We formulated a mathematical model (MM) to determine the GWG range that maximizes the likelihood of a healthy pregnancy (HP) if the recommendation is followed. We defined an HP as one where the mother has no complications such as pre-eclampsia, GDM, SGA, or LGA. Results: Forty-six percent of women had prepregnancy overweight or obesity. The prevalence of GDM, pre-eclampsia, SGA, and LGA were 3%, 1.2%, 9%, and 12%, respectively. An HP was present in 76% of pregnancies, 79% in the underweight group, 79% in normal weight group, 74% in the overweight group, and 67% in obese women. The GWG recommendations given by the MM (14-20 kg for underweight, 6-20 kg for normal weight, 9 -11 kg for overweight, and 6-7 kg for obese) led to higher probabilities of achieving an HP than the ones obtained with the IOM recommendations. Conclusion: The adoption of GWG recommendations based on characteristics of the Chilean population might lead to better short- and long-term health results for pregnant women. (C) 2018 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.