Phases of Labor

Labor is defined as progressive cervical dilatation in association with uterine contractions. Labor can be divided into the following stages:

Stage I: A) Latent phase

• Variable duration
• Starts at onset of labor
• Complete when the rate of cervical dilation increases (~ 3 cm)

B) Active phase (contractions every 2-3 mins, last 1 min, up to 70 mm Hg)

1. acceleration phase
2. phase of maximal slope
3. deceleration phase

• Normal active labor should progress 1 cm/hr
• Most common measure of uterine activity is the Montevideo unit (avg intensity frequency per 10 minutes)

Stage II: interval between maximal dilation and delivery (20-120 mins)

Stage III: placental delivery (5-20 mins)