Women may have another reason to eat healthy and exercise during pregnancy: These behaviors may lower their odds of having a cesarean section, a new meta-analysis finds. Gaining some weight during pregnancy is healthy and indeed expected, but gaining too much weight can have negative effects on both mom and baby. For example, gaining too much weight during pregnancy can increase the likelihood that a baby will have a high birth weight, which, in turn, can increase the baby's risk of medical issues, such as obesity and high blood pressure, during childhood.