Understanding the Stages of Labor
Normal labor is a continual, gradual process, marked by uterine contractions that lead to cervical dilation. Although it never seems subtle in the movies, diagnosing labor is not always as easy as it sounds. During the later weeks of pregnancy, strong and persistent contractions can occur, without progressive cervical dilation. Individuals experience and report the symptoms of labor differently, creating a challenge for those caregivers responsible for either getting the birthday party started, or sending home disappointed parents-to-be.
In order to study the labor process, it has been divided into three stages.
Stage #1: The first stage begins with the onset of labor and ends with full cervical dilation: 10 cm. This first stage is where most of a mother’s time in labor is spent; waiting for the cervix to dilate and managing the associated pain of contractions.
Stage #2: The second stage is the interval between full dilation and delivery of the infant. This is when the really hard work of labor happens-the pushing.
Stage #3: The third and final stage is the period between delivery of the infant and delivery of the placenta. Little attention is paid to this stage by most parents, as they are usually distracted by the results of the previous stage!
The progress of spontaneous labor has been studied across populations and has been found to be quite consistent among various ethnic groups, but significantly different between those who have had a delivery previously (multiparous women) and those who have not (nulliparous women).
Stage #1
The first stage has three phases relating to the speed at which the cervix dilates: the latent phase, the active phase and a transition phase. The latent phase is the most variable, and is simply defined as the period between the onset of labor (difficult to pinpoint for many women), and the start of the active phase, which is associated with a more rapid rate of cervical change. The latent phase involves physiologic changes to the uterine muscle and cervical connective tissue that allow it to be responsive to the signals of labor. These biochemical events can occur over a period of days to weeks, or even over a few hours, depending on the individual uterus.
The active phase usually begins by 2 to 4 cm of cervical dilation and is marked by acceleration in the “labor curve” which plots time (x-axis) against cervical dilation (y-axis). At this point, most women are experiencing longer and stronger painful contractions and are making their way to Labor and Delivery. Past studies of low-risk women who did not receive oxytocin or epidurals suggest the average length for active phase labor was close to 8 hours for nulliparas and close to 6 hours for multiparas, but the range of normal is anywhere from 2 to 20 hours. The transition phase occurs around 8 cm and is marked by intense contractions coming very frequently as the baby descends into the pelvis and the cervix fully dilates.
Stage #2
The second stage of labor involves the movement of the fetal head through the maternal pelvis and then the final expulsion of the fetus. As with the first stage of labor, the duration of this part of labor is dependent upon many factors, including the size of the infant, past deliveries, uterine contractions, and the size and shape of the mother’s pelvis. The duration of the second stage can be a few minutes to several hours, and is generally longer if the mother has an epidural. Frequently there is an increase in bloody mucus, as well as rectal pressure, a desire to defecate and the onset of nausea and vomiting. When the caregiver determines the time is right, the mother may start to push with contractions, adding the force of her abdominal muscles to the power of the uterine contractions.
Stage #3
After the delivery of the infant, the third stage of labor begins, which is marked by the separation and expulsion of the placenta from the uterus. This typically occurs within five to ten minutes after delivery of the infant, but may take up to half an hour.
Labor is an individual, gradual, and continuous process with no set time limits. As long as the mother and baby are doing well, patience is usually the best best medicine!