Background Information: Obesity is a substantial public-health crisis worldwide. This problem has also extended to the pregnant population with significant adverse pregnancy outcome. There is paucity of studies on impact of maternal obesity in Nigeria. Aim: To determine the impact of maternal obesity on pregnancy outcome in Abeokuta. Design: A cross-sectional analytical, multi centre study. Setting: Hospital setting, one tertiary and two secondary health facilities. Population Women delivering singleton babies between October 1, 2009 and December 31, 2009, at the study centres and who had booked for antenatal care before or by 20 weeks of gestation. Methods A total of 320 parturient in their 2nd day post partum were individually interviewed and the information entered into the data sheet. Some data were extracted from the case notes. The subjects were divided into two groups: Obese Group-BMI at booking ≥30 kg/m2 or the weight at any time in pregnancy ≥ 90 kg and Non Obese Group- BMI at booking <30 kg/m2 and the weight at any time in pregnancy <90 kg. Main outcome measures: Incidences of: previous perinatal loss, hypertension and diabetes mellitus in previous and index pregnancy, number of days on antenatal admission, duration of labour, delivery of low birth weight or a macrosomic baby, caesarean delivery perinatal death in the obese group and the respective odd ratios in reference to the non obese group.