This survey evaluated the effects of physical activity on gestational weight gain and birth weight of pregnant women attended by the Family Health Program in Campina Grande, Northeast of Brazil. A cohort study enrolling 118 pregnant women was conducted between 2005 and 2006. Evaluation of the initial nutritional status was performed following Atalah's criteria and gestational weight gain was evaluated according to the Institute of Medicine. The pattern of physical activity was evaluated according to METs (metabolic equivalent) and its association with weight gain and birth weight was determined. The predominant physical activity pattern at 16 weeks was mild, in 85.6% of pregnant women. An important reduction of physical activity levels was observed with evolution of pregnancy and 98.3% of pregnant women were sedentary at 24 weeks and 100% at 32 weeks. In the initial evaluation of nutritional status 50% were normal, 23% had low weight and 27% had overweight/obesity. At second and third trimesters about 45% of pregnant women had excessive weight gain. Adequate birth weight for gestational age was found in 85.6% of neonates but macrosomia was highly frequent (8.5%). A significant association between METs at 24 weeks and gestational weight gain was found in the second trimester (p=0.045). All the pregnant women were sedentary in the third trimester and a significant association between physical activity pattern and gestational weight gain was found in the second trimester, but there was no association between this pattern and birth weight.