Labor and Delivery

What is labor?

You are in labor when the muscles of your uterus contract so that your baby can be born. During labor, the uterine muscles tighten and the opening of the uterus (the cervix) thins and opens. The baby moves down the birth canal and is born. After delivery of the baby, the placenta also comes out of the uterus. This is the last part of labor.

Every labor is different. How long it lasts and how it progresses varies from woman to woman and from birth to birth. There are, however, general guidelines for labor that a health care provider uses to decide whether it is progressing normally. If it is not progressing normally, you may need medical assistance or surgery (a cesarean delivery).

If you have signs of labor before 37 weeks of pregnancy, the labor is considered preterm. You should call your health care provider right away if you have any signs or symptoms of labor before 37 weeks.

How does labor start?

No one knows exactly what starts the labor process. However, we do know that certain hormones, such as oxytocin and prostaglandin, cause uterine contractions and the thinning (effacement) of the cervix. Perhaps hormones from the baby trigger labor by stimulating the mother's hormone production.

The start of labor is defined as the time when regular uterine contractions cause the cervix to open and thin. There are some signs that your body is preparing for labor:

Passage of a small amount of blood-tinged mucus from the birth canal (vagina). This discharge is called "show" or the mucus plug. It may occur 1 day to several weeks before labor actually begins or it may happen after a vaginal exam.
A trickle or gush of water from the birth canal. This is caused by a breaking of the amniotic sac, also called the bag of waters. The amniotic sac surrounds the baby. If your bag of waters breaks, contact your health care provider right away and go to the hospital.

While the two signs above are clear warning signs that labor is about to begin, the sign that labor has begun is regular, strong contractions that:

are 2 to 3 minutes apart
last 30 seconds or longer and
cause the cervix to start to thin and open.

Sometimes knowing when labor has begun is difficult. You may be admitted to the hospital and then sent home if your labor does not progress--that is, if your cervix does not efface (thin out) or dilate (open). This is called false labor.

What happens during labor?

The 3 stages of labor are:

First stage: The cervix opens and thins.
Second stage: The baby moves through the birth canal and is born.
Third stage: The placenta passes through the birth canal and is delivered.

By the end of the first stage, the cervix has dilated fully to 10 centimeters (cm), or about 4 inches. The cervix needs to open this much for the baby to be able to pass through the birth canal. The first stage of labor is divided into early and active phases and usually lasts several hours.

Early labor, or prelabor, is when your cervix is 0 to 3 cm dilated. The contractions are irregular and mild.
Active labor begins when the cervix is 3 to 4 cm dilated. During active labor the contractions usually become stronger and more regular. The cervix dilates faster than during early labor. The average woman in her first labor may dilate about 1 cm per hour during the active phase of labor. If you have had a baby before, the cervix usually dilates faster than it did during your first delivery.

The baby is born during the second stage of labor. This is when you push the baby down the birth canal. This stage of labor usually lasts 15 to 75 minutes but may last as long as 2 or 3 hours, depending on several factors. These factors include previous births, the position of the baby's head, and the size of the baby and the birth canal. Sometimes medicine for pain, such as an epidural anesthetic, may slow labor at this stage.

During the third stage of labor you deliver the placenta. This usually happens within 30 minutes after the birth of the baby.

The first few hours after delivery are called postpartum recovery. During this time, the uterus continues to contract as it becomes firm and smaller. A small amount of bleeding continues and becomes less and less over a couple of days.

How are problems in labor identified?

Ensuring that your labor is normal requires skill, experience, and careful monitoring by your health care provider. Your vital signs, your uterine contractions, and your baby's heart rate must be checked throughout labor. These checks can be done manually or with an electronic monitor. They help your health care provider detect problems and take appropriate action.

During prenatal visits you and your partner should talk with your health care provider about any questions you have about labor. Discuss how you will manage pain (medicine, epidural, etc.). You should also talk about procedures, such as electronic monitoring, forceps, vacuum extraction, or cesarean section, which may become necessary during labor and delivery.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIA File WOM5247F.HTM Release 9.0/2006