Labor is a series of continuous, progressive contractions of the uterus that help the cervix dilate and efface (thin out). This lets the fetus move through the birth canal. Labor usually starts two weeks before or after the estimated date of delivery. However, the exact trigger for the onset of labor is unknown.
Signs of Labor
While each woman experiences labor differently, some common signs of labor may include:
Bloody show. A small amount of mucus, slightly mixed with blood, may be expelled from the vagina.
Contractions. Uterine muscle spasms that occur at intervals of less than 10 minutes may signify that labor has started. These may become more frequent and severe as labor progresses.
Rupture of the amniotic sac (bag of water). If you experience amniotic fluid gushing or leaking from your vagina, go to the hospital immediately and contact your health care provider. Most women go into labor within hours of the amniotic sac breaking. If labor does not begin soon after rupturing your amniotic sac, you will be given medications to induce your labor. This step is often taken to prevent infection and other delivery complications.
If you are unsure about the start of your labor, call your health care provider.
Different Stages of Labor
Typically, labor is divided into three stages:
First stage. During the onset of labor, your cervix will complete dilation. Early in this stage, you may not recognize that you are in labor if your contractions are mild and irregular. Early labor is divided into two phases:
The latent phase is marked by strong contractions that usually occur at five- to 20-minute intervals. During this phase, your cervix will dilate approximately 3 to 4 centimeters and efface. This is usually the longest and least intense phase of labor. You may be admitted to the hospital during this phase. Your doctor will perform pelvic exams to determine the dilation of the cervix.
The active phase is signaled by the dilation of the cervix from 4 to 10 centimeters. Your contractions will likely increase in length, severity and frequency, occurring at three- to four-minute intervals. In most cases, the active phase is shorter than the latent phase.
An illustration of the first stage of labor.
Second stage. Often referred to as the pushing stage of labor, this stage starts when your cervix is completely opened and ends with the delivery of your baby. During the second stage, you become actively involved by pushing the baby through the birth canal. Crowning occurs when your baby’s head is visible at the opening of the vagina. The second stage is usually shorter than the first stage, and may take between 30 minutes and three hours for your first pregnancy.
Third stage. After your baby is delivered, you will enter the third and final stage of labor. This stage involves the passage of the placenta (the organ that nourished your baby inside of the uterus) out of the uterus and through the vagina. The delivery of the placenta may take up to 30 minutes.
Since each labor experience is different, the amount of time required for each stage will vary. If labor induction is not required, most women will deliver their baby within 10 hours of being admitted to the hospital. Labor is generally shorter for subsequent pregnancies.