Some women don't even realize they are in the first stage of labor, mistaking it for gas, heartburn, backache, or indigestion. There are three signs that labor has begun. They do not necessarily occur in any particular order and they may occur in a different order with each pregnancy. Contractions occur because your uterus is tightening and relaxing to help open the cervix and push the baby out through your birth canal. During the early part of labor this may feel like menstrual cramps.
Some women feel only abdominal contractions or only a backache.
Contractions of true labor occur regularly. They usually start about 15 to 20 minutes apart and last 30 to 45 seconds. As your labor proceeds, the contractions become more frequent and last about 60 seconds. If you walk around or lie down they will not go away as they did in false labor. Also, there is generally a small amount of blood.