Pregnant women who exercised regularly before pregnancy can continue to exercise, if they take a few precautions. As long as you are in good health, not at risk for miscarriage and do not engage in strenuous exercise, a pregnant woman can enjoy regular physical exercise. Women who have not been physically active or engaged only in light, occasional physical activity before pregnancy should not start an exercise program more strenuous than walking. You are going to need strength and stamina to get through your pregnancy and delivery. Check with your doctor before beginning or continuing any exercise program. Women who are pregnant may benefit from light exercise in many ways. Walking and stretching exercises can help to relieve low back pain and prevent excessive weight gain. Swimming is a whole body aerobic exercise that most pregnant women can safely do throughout pregnancy to remain fit and control weight gain. Excess weight gain during pregnancy can contribute to gestational diabetes, high blood pressure and may even contribute to postpartum conditions like depression. Pregnant women who experience pregnancy-related conditions or are at risk for certain conditions should not exercise except on the advice and supervision of their doctor. Those who are at risk and should avoid exercise include women who are at risk for miscarriage or who have had a miscarriage in the past, history of premature delivery, bleeding or spotting and those with weak cervix or low placenta. Stretching exercises are especially helpful to maintain muscle tone and help to maintain flexibility. Stretching is important before other exercise, including walking, using a treadmill or swimming, to help reduce the risk of muscle strain. 

Begin a stretching exercise session with your neck and work your way to your feet. Sit in a comfortable chair or sit on the floor in a comfortable position. Place your hands on your thighs palms down and sit up straight and tall. Relax your shoulders and  your neck, and then drop your chin forward toward your chest. Rotate your whole head toward your right shoulder and then back to the middle of your chest. Continue rotating to the left shoulder and then back to your chest. Repeat this stretching exercise 5 times. 

Stretch your arms and shoulders to help relieve upper back stress and energize your whole body. Sit up straight, drop your shoulders down and back to straighten your back. Stretch your right arm forward and lean to the right stretching toward your fingertips. Return your right arm back to your side and then stretch forward with your left arm, and lean forward with your body stretching toward your left fingertips. Alternate back and forth in a swimming motion. Repeat this exercise for 10 repetitions. 

Kegel exercises during pregnancy strengthen the muscles of the abdominal floor that support the uterus, intestines and bladder. Sit in a comfortable chair with your feet flat on the floor and your arms relaxed at your sides. Sit up straight, tighten the muscles of your pelvic floor and then relax the muscles. To tighten the muscles in your pelvic floor, pretend that you are trying to stop the flow of urine midstream. Squeeze the muscles that you would use to stop your urine. Perform Kegel exercises anytime of the day, as often as you want, but try to do at least 10 sets of five contractions each day. Hold each muscle contraction for 5 to 8 seconds. Remember to breathe when doing Kegel exercises and do not contract your abdominal muscles while performing this exercise. 

Walking is a safe, effective form of aerobic exercise that can help a pregnant woman control her weight gain, remain physically fit and feel energized. Take extra precautions when walking while pregnant to avoid falls. Walk on smooth, flat areas such as sidewalks and walking trails. Do not walk when your path is covered in snow, ice or rain, which can make surfaces slippery and may result in a fall. Walk with a partner or a friend and avoid overexertion. A 20 to 30 minute walk every other day is generally safe for most pregnant women. 

For more information about safe exercises during pregnancy, see:

Mayo Clinic, Pregnancy and Exercise: Baby, Let’s Move!