The Stages of Labor Health Article

First Stage

The first stage of labor is defined as the interval between the onset of labor and complete dilation of the cervix. This stage is further subdivided into three phases: latent, acceleration, and deceleration. The acceleration and deceleration phases are sometimes combined and called the active phase.

Dilation Of The Cervix

The course of labor through the first stage can be analyzed by graphing how much the cervix dilates over time. The rate of cervical dilation determines whether the first stage of labor is normal. The cervix takes longer to dilate in women having their first vaginal delivery than in women who have had a previous vaginal delivery.

Latent Phase

The latent phase is the earliest part of the first stage of labor and is defined as the period between the onset of labor and the point at which cervical dilation begins to rapidly change. Defining the latent phase can be difficult because some women begin having contractions hours, days, and even weeks before actual cervical dilation occurs. Furthermore, some women have cervical dilation of three centimeters or more before they feel any contractions. During the latent phase the cervix thins out, or effaces. The time spent in the latent phase varies between women and pregnancies and is dependent on the number of previous labors.

Active phase

The active phase of labor begins when cervical dilation begins to change consistently. For women delivering for the first time, this generally occurs when the cervix is fully, or 100% (see diagram above), effaced and 3 to 4 centimeters dilated. Cervical dilation then continues at a minimum of 1.2 centimeters per hour, on average. For women with previous vaginal deliveries active labor may occur before the cervix is fully effaced and then progresses at a minimum of 1.5 centimeters per hour. Once again, the onset of the active phase varies greatly between women and pregnancies. This phase ends when cervical dilation is complete at about 10 centimeters.

Second Stage

The second stage of labor is defined as the period from complete cervical dilation to the delivery of the baby. Technically, the second stage begins with complete cervical dilation. However, timing of the second stage does not begin until the mother starts to push. The combined effort of the uterus contracting and the mother pushing causes the baby to descend through the birth canal. If a woman chooses to have an epidural, which blocks pain sensations, motor function, and pressure sensations, the second stage of labor may last up to an hour longer because she cannot push as well with the epidural block. More recent studies have suggested that a second stage of four or more hours may be safe if there is no evidence of fetal or maternal complications, indicating that there should not be a rush to perform a cesarean section or forceps delivery solely based on time.

In an effort to reduce the number of unnecessary forceps, vacuum, and cesarean deliveries performed because of a prolonged second stage, a technique known as rest and descend has been employed. Used by midwives for years, it is now finding its way into the practices of many obstetricians and family physicians. The rest and descend method is especially helpful in women who have an epidural block and cannot push. It involves waiting and resting without pushing, even after cervical dilation is complete, until the mother feels the urge to push. The rest and descend method is not appropriate if the mother or baby appear to be compromised in any way, and it requires a patient obstetrician.

Third Stage

The third stage is between delivery of the baby and delivery of the placenta. Unlike the other stages of labor, the duration of the third stage is usually the same for all women. On average, it lasts about five minutes and should be considered prolonged if it lasts longer than 30 minutes. During this stage, the mother is at risk for heavy blood loss due to postpartum hemorrhage if the placenta does not separate from the uterus properly.

To learn more, go to What Happens During Labor?.

Then continue to Abnormal Labor, Inducing Labor, and Pain Relief During Labor.