This will be an open randomized clinical trial involving pregnant women between 35 and 37 weeks randomized to two modalities of exercise: treadmill or stationary bike. The study hypothesis is that exercise on a stationary cycle causes less maternal and fetal effects in relation to treadmill exercise.We will study the acute effects of exercise for both the mother and the fetus, monitoring the parameters before, during and after exercise for 20 minutes. The exercise intensity will be moderate, remaining between 60% and 80% of maximum heart rate. Women will be monitored with a recording equipment of ABPM (ambulatory blood pressure monitorization) and continuous cardiotocography and blood will be collected to measure blood glucose, total cholesterol and HDL, nitrate and lactate before, during and after exercise. The analysis variables are: maternal heart rate and blood pressure, fetal heart rate, number of fetal movements, transient accelerations, decelerations, short-term variability, episodes of high variability, uterine tone, glucose, lactate, nitrate, total cholesterol and HDL.The analysis will be based on intention to treat, according to the recommendations of the CONSORT (2010).