OBJECTIVE: Excessive weight gain during pregnancy has an important influence on fetal growth and on weight development in future generations. DESIGN AND METHODS: We performed a prospective cohort study of 325 obese and non-obese Caucasian women with naturally conceived, singleton pregnancies. They were followed up until delivery for maternal weight gain and for fetal growth with ultrasound based weight estimations and final birth weight. Using cluster analysis distinct profiles of maternal weight gain during pregnancy were obtained. Longitudinal regression analysis was performed to investigate the relationship of the maternal weight gain profile and body mass index (BMI) on fetal growth and final birth weight. RESULTS: Cluster analysis revealed four discernable maternal weight gain profiles: twelve cases (3.7%) ended up at their starting weight or decreased in weight (cluster 1), 16 cases (4.9%) that slightly increased in weight (maximum 4 kg) as compared to their initial weight (cluster 2), 114 cases (35.1%) that gained between 4 and 12 kg in weight (cluster 3) and 183 cases (56.3%) that showed the largest weight gain: more than 12 kg (cluster 4). There were statistically significant differences in fetal growth associated with weight gain cluster which became apparent late in the second trimester and increased towards the end of pregnancy. Maternal BMI and maternal weight gain profile were independent predictors of fetal growth and birth weight. CONCLUSIONS: Therefore we conclude that cluster analysis permits to discern four gestational weight gain patterns in obese and non-obese subjects and that both maternal BMI and maternal weight gain pattern during pregnancy positively influence fetal growth and birth weight.