Introduction and objective. - Gestational weight gain (GWG) has been reported to be associated with pregnancy outcomes. The aim of this study was to evaluate the effects of GWG on maternal and birth complications. Materials and methods. - A prospective and longitudinal cohort study was conducted among pregnant women who had attended antenatal centers in Constantine, Algeria, between 2013 and 2015. Two hundred pregnant women aged 19 to 41 years old were followed for 9 months of pregnancy. They underwent body weight measurement during routine examination at first, second and third trimester. GWG was categorized as below, within or above the Institute of Medicine (IOM) (2009) recommendations. Data included age and parity. Pregnancy outcomes were analyzed in relation to GWG. Results. - Mean GWG was 8.9 +/- 5.4 kg. Among all subjects, only 27.5% of women had gained the recommended amount of weight, with 48.5% gaining less than recommended, and 24.0% gaining more than recommended by the IOM. High birth weight was significantly more frequent in women with excessive weight gain, compared to those with normal gain (27.1% vs 14.5%, P = 0.04). The percentage of low birth infants was statistically very high in pregnant women with excessive weight gain, compared to women with normal gain (14.6% vs 3.6%, P = 0.04). The risk of gestational hypertension increased with excessive GWG (P < 0.01). Conclusion. - The pregnancy and birth outcomes depend on the women's gestational weight gain. (C) 2018 Association pour le developpement de la recherche en nutrition (ADREN). Published by Elsevier Masson SAS. All rights reserved.