Pregnant women can exercise to strengthen the muscles of the core that help to stabilize the spine and thereby minimize back pain and discomfort, according to Jessica Matthews, an assistant professor of health and exercise science at Miramar College in San Diego and pregnancy fitness educator. Matthews recommends limb raises to reduce the strain on your back. Begin in a hands and knees position and slowly lift your left arm out while lifting your right leg for eight seconds. Switch to your right arm and left leg and repeat the exercise to engage your core back muscles while keeping your spine in a neutral position. Pool exercises, such as water aerobics, can also help relieve the pressure on your lumbar spine, says Matthews who is also an exercise physiologist.