Labor is a series of regular uterine contractions that open the cervix and push the baby out. The hormone oxytocin drives the contractions in a feedback loop that makes them stronger.
First stage
From the start of regular contractions until the cervix is fully dilated at 10 cm. It has a slow latent phase and a faster active phase that usually starts around 6 cm.
Second stage
From full dilation until the baby is born. The head flexes, rotates and extends to pass through the pelvis, helped by the mother pushing.
Third stage
From the birth of the baby until the placenta is delivered, usually within 30 minutes. Signs of separation include a gush of blood and lengthening of the cord.
After birth
The uterus contracts firmly to squeeze shut the vessels where the placenta was attached. A soft, boggy uterus is the most common cause of postpartum hemorrhage.
| Stage | Starts | Ends |
|---|---|---|
| First | Regular contractions | Cervix fully dilated (10 cm) |
| Second | Full dilation | Birth of the baby |
| Third | Birth of the baby | Delivery of the placenta |
At the bedside
During labor, track the contractions and the fetal heart rate, and watch the tracing for decelerations. After birth, check that the fundus is firm and massage it if it is boggy.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).