Medical Specialties: Emergency medicine, Obstetrics/gynecology

Clinical Definition

The natural and physical process of delivering a baby from the uterus, followed by the placenta, is known as labor. It involves contractions of the uterus and effacement and dilation of the cervix, which allows for passage through the birth canal. Labor is triggered by the pituitary gland hormone oxytocin, which starts uterine contractions. Several stages and phases describe labor from beginning to end. 

In Our Own Words

Labor is the process of giving birth. The hormone oxytocin starts the regular, painful contractions, which are just one part of labor. The hormones and uterine contractions of childbirth also lead to a “ripening” of the cervix, causing it to thin out and dilate, which ultimately allows the baby to move through the birth canal.


The first stage of labor generally lasts the longest, especially so for first-time Moms -- dilation and thinning of the uterine cervix. The second stage is the delivery of the baby. The third stage is the delivery of the placenta.

Relevant Conditions
  • Pregnancy
  • False labor (Braxton Hicks)
  • Epidural
  • Episiotomy
  • Cesarean section
  • VBAC
  • Natural childbirth
  • Induction
Common Types
  • Term
  • Pre-term
Side Effects
  • Uterine contractions
  • Lower back pain
  • Amniotic sack breaks (water breaks)
  • Red or browns mucus discharge (bloody show)
Share this article
  • U.S Department of Health and Human Services. "Pregnancy Labor and Birth." Accessed November 2013.
  • UCSF Medical Center. "Pregnancy Labor and Delivery." Accessed November 2013.
  • University of Maryland Medical Center. "The Three Stages of Labor." Accessed November 2013.
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