 Gestational diabetes mellitus GDM is increasing worldwide and has been associated with adverse perinatal outcomes and high risk for chronic disease both for the mother and for the child. Physical exercise is feasible to diabetic pregnant women and contributes to a better glycemic control and to decrease adverse perinatal outcomes. However there are no randomized controlled trials RCT assessing the effects of aquatic physical exercise on GDM control and adverse maternal and fetal outcomes. 