Merck Manual

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Stages of Labor
Stages of Labor

Initial (Latent) Phase

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

Discomfort is minimal.

The cervix begins to thin and opens to about 1 1/2 inches (4 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 12 hours) in subsequent pregnancies.

In these topics
Cervical Insufficiency Labor