For healthy pregnant women who aren't very active, doing structured exercise three times a week plus some coaching about staying active doesn't seem to help them gain less weight by the time they give birth, compared to just getting regular prenatal care.

For healthy pregnant women with a normal weight, doing structured exercise or getting motivational counseling doesn't seem to change their chances of getting gestational diabetes, high blood pressure during pregnancy, having a baby too early, or the baby's weight at birth.

Even when pregnant women with a normal weight are given exercise programs or motivation tips, most still don't get enough physical activity during pregnancy — they're still moving less than the recommended amount each week.

If pregnant women do supervised strength training once or twice a week for at least 12 weeks, they might gain about 4 pounds less than those who get regular prenatal care, and this could help lower their chances of developing gestational diabetes, high blood pressure, or needing a C-section.

Being active during pregnancy is generally safe and helps most women feel better, stay fit, manage their weight, lower their chance of getting gestational diabetes (especially if they're overweight), and feel less stressed — so doctors often recommend it for healthy pregnancies.

We don't yet know the best way for pregnant women to exercise—how hard, how often, or what kind of support helps most—and we also need to understand if working physically while pregnant affects the mom and baby's health.