Introduction: The pathologies associated with excessive weight gain during pregnancy are numerous and frequent. They are the cause of significant maternal and perinatal morbidity and mortality and thus pose a real public health problem. Patients and method: The main objective of our work was to study the influence of excessive weight gain on maternal and perinatal morbidity and mortality in a university hospital in Cotonou. Study method:The study took place at the CUGO. This was a descriptive and analytical study with retrospective data collection over a period of 10 years from January 1, 2012 to December 31, 2021. The analysis focused on the description of pregnant women and the search for factors associated with an excessive weight gain during pregnancy and which influence maternal and perinatal prognosis. The different odds ratios and their confidence intervals were calculated. The significance level was 5%. Results: A total of 690 pregnant women were included and divided into four sub-populations according to their pre-gestational or first trimester BMI: 05.94% underweight pregnant women, 41.74% normal BMI pregnant women, 28.55% of overweight pregnant women and 23.77% obese pregnant women. The average age of pregnant women was 30.41 years ± 5.40 years. They were civil servants (35.80%) and resided in Cotonou in 93.91% of cases. Pregnant women had a history of hypertension in nearly 3% of cases. Pregnancy hypertension (07.97%) was the main pathology associated with pregnancy in our study. Weight gain was excessive in overweight pregnant women and obese pregnant women in the same proportion 41.12%. The average weight gain was 9.42 kg for underweight pregnant women, 8.35 kg for pregnant women with a normal BMI, 8.46 kg for overweight pregnant women and 7.45 kg for obese pregnant women. Pregnant women who had gained ex-