Early labor can last up to 12 hours, and it is the stage of labor when the cervix becomes completely effaced and dilates to 3 centimeters with contractions lasting up to 45 seconds and coming every 5 to 30 minutes. Early labor is followed by active labor, which lasts up to 5 hours or until the cervix dilates to 7 centimeters; contractions in active labor last up to 60 seconds and may be anywhere from 3 to 5 minutes apart, notes the American Pregnancy Association, or APA.
The third phase of labor is called the transition phase, and it lasts from 30 minutes up to 2 hours, ending when the cervix is dilated to 10 centimeters. During transitional labor, contractions may last up to 90 seconds and be up to 2 minutes apart, according to the APA. The final stage of birth ends with the delivery of the placenta.
The APA points out that no two deliveries are the same, and that there is no reliable means of predicting how long labor will last or how it will go. The stages of labor are described by the APA in general terms; each pregnant woman has a unique experience when giving birth.