Doing yoga in a gentle way will help you keep your body active and reduce morning sickness and constipation. But while your pregnant do not overstretch the abdomen; the emphasis of your twisting poses should be on the shoulders and upper back. Its adviced to do standing yoga poses during frist trimesters. While during the second and third trimester, you need to focus more on breathing exercise and meditation. However, it is also not recommended to practice from the tenth through the fourteenth week of pregnancy since these are crucial times.