Initial (Latent) Phase

Contractions are irregular at first but become progressively stronger and more rhythmic.

Discomfort is minimal but may increase over time.

The cervix begins to thin and dilates to about 4 to 5 centimeters.

The initial phase lasts an average of 8 hours (usually no more than 20 hours) in a first pregnancy and 5 hours (usually no more than 14 hours) in subsequent pregnancies.