A new study shows that moderate exercise is safe during pregnancy, and it can help prevent childhood obesity and diabetes. In the study, published in the journal PLoS ONE, Brazilian researchers collected data on leisure-time physical activity for pregnant volunteers. Each woman reported her exercise during the second and third trimesters of pregnancy. The researchers weighed the women throughout the study and weighed the babies at birth. They found that getting at least 150 minutes of exercise per week, or roughly 20 minutes each day, was associated with a decrease in the baby’s birth weight, which reduces the risk of childhood obesity and diabetes, without raising the risk of the baby being born with too little weight for their gestational age.