Prenatal yoga classes generally offer gentler, less strenuous sequences of poses and a greater use of props to support the body in poses. Your teacher may offer a number of variations and use props (belts, bolsters, blocks, or chairs) to make poses comfortable and available to you during each stage of your pregnancy; you may also use more props as your baby grows. What you won't -- and shouldn't -- see in prenatal classes are elevated temperatures (as in "hot yoga" classes) because they put you at risk for lightheadedness, dehydration, and other complications. You also won't see certain categories of poses, like those that require you to lie on your back or twist deeply, as they can put pressure on your organs and major blood vessels in a way that could be unsafe for your baby.
A skilled instructor will offer a sequence of poses that are designed to meet all the students' needs. Regardless of which stage of pregnancy the student is in, prenatal yoga poses generally target the back, particularly the lower back, an area that is especially vulnerable to pain and injury as a growing belly and shifting center of gravity tug the spine out of its natural curvature.
Certain poses should be avoided.. Many forward bends can compress the belly too much. Twists and poses that are meant to strengthen the abdominal muscles are also not advised because they can put too much stress on the rectus abdominus muscles, the muscle group that runs straight up and down your abdomen, and lead it to separate, which may cause future back pain and the need for physical therapy to help repair the separation. Balancing poses should be done with care, or against a wall or other strong support, to avoid the risk of falling.
Prenatal yoga classes offer a balanced sequence of joint mobility exercises, seated postures, standing postures, hip openers, breathing, and relaxation exercises -- leaving out the contraindicated postures, but still offering a balanced practice.