Usually labor pains are a little stronger version of period pains. In women who don't have very strong period pains, maybe from 36 weeks, pregnant women might experience some cramping and backache, especially when the baby is kicking hard or while exercising. When the cramps increase or the intensity is getting more stronger then it could be that labor has begun. Dr. Chitralekha Dambekodi explains how to identify labor through various symptoms experienced by a pregnant woman. For more information, visit care.com