It is common on the labor and delivery ward to hear the nurses and doctors tell patients that they cannot have an epidural until cervical dilation reaches 4 cm. The reasons given for this include that labor will be prolonged, cesarean section rates increased, or that pain relief is just not needed before that point. In stark contrast is the American College of Obstetrician and Gynecologists (ACOG) recommendations that timing of epidural analgesia for labor and delivery is when the patient asks. That said, what are the impacts of epidural analgesia on labor and delivery?

The stages of labor are typically divided into the first, second, and third stages of labor. The first stage of labor can be separated into the early and active phases. Traditionally, early labor involves the onset of contractions and cervical dilation until 4 cm. The next portion of the first stage is known as the active phase and involves the cervix dilating from 4 to 10 cm. The second stage of labor is from complete cervical dilation until birth. The third stage of labor is from the time of birth until delivery of the placenta. In 1993, Thorpe published a paper stating that there was an increased risk of dystocia in nulliparous women who had epidural analgesia for labor prior to cervical dilation of 4 cm. This is where the “no epidural until after 4 cm” idea originated. Subsequently, in several well-designed randomized clinical trials, Chestnut showed this not to be the case. Since the 1990s, clinical studies have not shown that epidurals increase the cesarean section rate, so we can reassure our patients that the available evidence does not support delaying pain relief due to fear of increasing a woman’s risk of cesarean section.

However, epidurals may affect the duration of labor. That is, the placement and use of an epidural for labor and delivery may prolong the first and second stages of labor. Typically, the first stage may be prolonged up to 40 minutes. Failure to progress should not be defined until the patient has achieved the active stage of labor. During the active stage, a number of indices are used to define failure to progress; however, epidural analgesia has not been associated with failure to progress to the second stage of labor. The second stage of labor has been reported to be 15 to 36 minutes longer with the use of epidural analgesia. The ACOG suggests that a prolonged second stage of labor should be considered when the second stage exceeds 3 hours
if regional anesthesia is administered or 2 hours in the absence of regional anesthesia in nulliparous women. In multiparous women, such a diagnosis can be made if the second stage of labor exceeds 2 hours with regional anesthesia or 1 hour without. There is no significant prolongation of the third stage of labor with epidural analgesia.