BACKGROUND INFORMATION: The goal of antenatal care is to ensure mothers receive the best care and information with the intention of having a safe and successful delivery. One of the means of achieving this is to ensure that mothers get the best nutrition in pregnancy and an objective way of monitoring this is through monitoring weight gain in pregnancy. However, this is affected by several factors including pre-pregnancy body mass index especially if underweight, overweight or obese. All these interact to determine the foetomaternal outcome of pregnancy. AIM: To investigate the association between Gestational weight gain and foetomaternal outcome at Federal Medical Centre, Abeokuta. DESIGN: A prospective cohort study. SETTING: Department of Obstetrics and Gynaecology, Federal Medical Centre, Abeokuta. POPULATION: Women with singleton foetus registering for antenatal care before or at 20 weeks gestation and delivering between February 1, 2013 and September 30, 2013 at the study centre. METHODS: A total of 352 patients were recruited at presentation for antenatal care booking and followed up till discharge (post-delivery) from the postnatal ward. The babies’ data were also recorded. The subjects were divided into four groups based on pre-pregnancy body mass index: Underweight (<18.5kg/m2 ); Normal Weight (18.5-24.9kg/m2 ); Overweight (25- 29.9kg/m2 ) and Obese (≥30kg/m2 ) MAIN OUTCOME MEASURES: Maternal morbidity in pregnancy, mode of deliverycaesarean or vaginal delivery, delivery of low birth weight, normosomic or a macrosomic baby, perinatal morbidity and perinatal death in each of these groups was looked into.