Labor normally begins when a fetus is sufficiently mature to survive outside the uterus, yet not too large to cause difficulties during birth. Contractions of the uterus and changes in the cervix prepare the body for delivery. Some signs that labor is imminent include lightening, increased energy, slight weight loss, backache, and Braxton Hicks contractions. True labor involves regular, intensifying uterine contractions and cervical changes like effacement and dilation that allow the baby to pass through the birth canal. Understanding the signs of true labor helps prevent premature birth and helps the woman recognize when labor begins.