What Is Labor in Pregnancy?

There are three stages of labor, as outlined below.

1. Stage 1— Early labor

• Cervix dilates completely, but if contractions are mild or irregular it may not be noticeable
• There are two phases of this stage:
  • Latent phase
    • Strong contractions occurring at five- to 20-minute intervals
    • The cervix will dilate about 3 to 4 centimeters and thins, shortens, and softens (effaces)
    • Tends to be the longest and least intense phase of labor
    • Hospital admission may occur during this phase
  • Active phase
    • Cervix dilates from 4 to 10 centimeters
    • Contractions usually increase in length, severity, and frequency, and occur at three- to four-minute intervals
    • The active phase is usually shorter than the latent phase

2. Stage 2 — Pushing stage

• Starts when the cervix is completely opened and ends with the delivery of the baby
• The mother is actively involved pushing the baby through the birth canal
• Crowning occurs when the baby’s head is visible at the opening of the vagina
• This stage is usually shorter than the first stage, and may take between 30 minutes and three hours for a first pregnancy

3. Stage 3 — Final stage

• Passage of the placenta out of the uterus and through the vagina
• May take up to 30 minutes

Common signs of labor may include:

• Back pain 
• Bloody show
  • A small amount of mucus mixed with a little blood may pass from the vagina
• Contractions
  • Uterine muscle spasms can signify the start of labor and may become more frequent and severe as labor progresses
• Rupture of the amniotic sac (often referred to as the “water breaking”)
  • Amniotic fluid leaks through the cervix and vagina
  • Labor usually occurs within hours of the amniotic sac breaking
  • If labor does not occur after the water breaks and the baby is due, labor is usually induced to reduce the risk of infection

Sometimes, labor must be induced, or stimulated, to begin. Labor is typically not induced before 39 weeks of pregnancy unless there is a problem. 

Common reasons for induction include:

• There is a risk to the mother or fetus due to complications
• The pregnancy is far past the due date
• The mother has preeclampsia, eclampsia, or chronic high blood pressure
• The fetus has been diagnosed with poor growth

There are several techniques to help induce labor when needed, such as: 

• Insertion of vaginal suppositories that contain prostaglandin to stimulate contractions
• An intravenous (IV) infusion of oxytocin (a hormone produced by the pituitary gland that stimulates contractions) or a similar drug
• Artificially rupturing the amniotic sac