During which phase does the cervix dilate from 4-7 cm?

The active phase of labor is characterized by the dilation of the cervix from around 4 cm to 7 cm. During this phase, contractions become more frequent, intense, and regular, typically occurring every 3 to 5 minutes and lasting about 45 to 60 seconds. This phase generally follows the latent phase, which involves the cervix dilating from 0 to 3 cm, where contractions may be more irregular and less intense.

In contrast, the transition phase occurs immediately after the active phase and involves further dilation from 7 cm to 10 cm, during which the intensity of contractions peaks and often leads to significant discomfort. The second stage of labor begins once the cervix is fully dilated at 10 cm and involves the descent and birth of the baby.

Understanding the distinct characteristics of each phase helps clarify why the active phase is defined by this specific range of dilation.