The transitional phase, which lasts 1 to 3 hours, is the shortest but most difficult part of the first stage of labor. This phase is characterized by intense uterine contractions that occur every 1 to 2 minutes and last 45 to 90 seconds. The active phase lasts 4 to 6 hours; it is characterized by contractions that starts out moderately intense, grow stronger, and last about 60 seconds. The complete phase occurs during the second, not first, stage of labor. The latent phase lasts 5 to 8 hours and is marked by mild, short, irregular contractions.