Up to 3 centimeters of dilation is considered early labor, and this phase of labor lasts from eight to 12 hours, according the American Pregnancy Association. During this phase contractions are typically mild and irregular.
During early stages of labor, the amniotic sac often ruptures, according to American Pregnancy Association. When the cervix is dilated from 4 to 7 centimeters, this phase is called active labor. As the transition occurs to active labor, contractions become closer together. This is typically the time that a woman heads to the hospital or birthing center. The transition phase is the final phase of labor and occurs when the cervix is 8 to 10 centimeters dilated.