Labor

Labor is defined as the onset of painful uterine contractions that lead to cervical change, and it may be divided into three stages.

1. The first stage begins with the onset of regular contractions and ends with full cervical dilation. It is divided into a slow latent phase and a rapidly progressive active phase characterized by accelerated cervical dilation. Patients with body mass index greater than 30 kg/m² and male fetuses may experience prolonged first stage of labor. Such factors highlight the limitations of widespread use of a single labor curve for all patients.
2. The second stage extends from full cervical dilation until delivery of the infant.
3. The third stage begins after delivery of the infant, ending with delivery of the placenta.