## Stages of Labor: Definitions and Boundaries **Key Point:** Labor is divided into three distinct stages, each with precise anatomical and temporal boundaries. ### The Three Stages of Labor | Stage | Boundary Markers | Duration (Primigravida) | Key Events | |-------|------------------|------------------------|-------------| | **First** | Onset of labor → Full cervical dilation (10 cm) | 12–18 hours | Cervical effacement and dilation; three phases (latent, active, deceleration) | | **Second** | Full cervical dilation → Delivery of fetus | 30 min–2 hours | Descent and rotation of fetal head; maternal pushing; fetal expulsion | | **Third** | Delivery of fetus → Delivery of placenta | 5–30 minutes | Placental separation and expulsion; hemostasis | **High-Yield:** The second stage begins immediately after full cervical dilation (10 cm) is confirmed and ends with the complete delivery of the baby. This is the "pushing stage" where the mother actively participates in expelling the fetus. **Clinical Pearl:** The second stage is further subdivided into: - **Latent phase** (passive descent): fetal head descends without maternal effort - **Active phase** (active pushing): mother pushes with contractions; rapid descent and delivery **Mnemonic:** **FST** = **F**irst (dilation), **S**econd (delivery of baby), **T**hird (delivery of placenta). [cite:Williams Obstetrics 25e Ch 22]
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