Protracted and Prolonged Labor
“Failure to progress” is a common concern of pregnant women who wish to avoid a cesarean section. Formally called dystocia, it has been suggested that this term should be renamed and redefined to protracted latent phase of labor (first stage – dilation) and prolonged active phase of labor (second stage – pushing), which better reflects current research showing that women labor and dilate at varying rates.
This updated research and relaxed definition allows for more caution in the diagnosis of slow labor, and gives women more time to labor down, rest, change positions, and focus on pushing – as long as the baby shows no signs of distress.
All women – no matter what their birth plan is – should be aware of the methods and options for augmentation of labor in the event they are recommended due to protracted or prolonged labor. This way, women have time to understand the process, the methods used, the risks and benefits of each, and have plenty of time to ask their HCP questions. They will also feel more confident in their decisions and have a better understanding of why certain options are used and when.
Background
Labor dystocia, commonly known as “failure to progress”, is defined by the American College of Obstetricians and Gynecologists (ACOG) as “slow, abnormal progression of labor” that may ultimately lead to augmentation methods to boost labor (oxytocin, amniotomy) or cesarean delivery.
However, in 2014 (and reaffirmed in 2019) the ACOG indicated that it may be necessary to revisit the definition of labor dystocia because recent data show that contemporary labor progresses at a rate substantially slower than what has been taught in the past.
Suggested updates include that the management of the first stage of labor (0 to 10 centimeters) should be referred to as a protracted latent phase of labor (1 to 4 or 6 cm) or protracted active phase of labor (4 or 6 to 10 cm) rather than “abnormal”. A lengthy second stage of labor (full dilation to delivery) is categorized as prolonged.
Note: Whether the active phase of labor begins at 4 or 6 cm is debated. Previously, the active phase of labor was determined to start at 4 cm dilation. Newer research indicates some women may not enter the active phase until 6 cm (read Dilation and Effacement).
Slow labor progress from 1 cm to 4 or 6 cm dilation: Protracted latent phase
Slow labor progress from 4 or 6 cm to full dilation: Protracted active phase
Slow labor progress from full dilation to delivery: Prolonged second stage
Causes
If a woman is presenting with a protracted or prolonged labor, the HCP will perform an assessment of all possible causes to determine the best path forward; most options depend on fetal signs of well-being.
The most significant cause is an ineffective pattern of contractions, which can affect both the dilation and pushing stages. Contractions influence both the location of the baby’s head and cervical dilation, and an ineffective pattern can stall labor progress. Contractions can be either too weak or too infrequent (hypotonic), or too strong or too close together (hypertonic).
Slow dilation is also a cause of protracted labor. However, cervical dilation is highly individualized and is affected by several variables, not just contraction pattern. Further, there is no definitive minimum amount of time during labor in which all women are expected to fully dilate.
The rate of cervical dilation (cm/hr) in the first stage of labor forms the basis of decision-making by the HCP as to how delivery will proceed. For example, the HCP may determine that dilation may be too slow, and will decide to augment labor through oxytocin or amniotomy – which is a common practice called active management of labor (usually to avoid a cesarean delivery).
Under active management, the slowest acceptable rate of dilation is defined as 1 cm/hr; therefore, women with dilation rates under this are more likely to receive oxytocin even with reassuring fetal health signs. However, it is currently assessed that 1 cm/hr, especially in first deliveries, may be unrealistically fast, and women should be given more time to dilate without augmentation methods (if desired) as long as the baby shows no signs of distress.
Read more on dilation rates here.
Obstructed labor occurs when despite strong pushing and regular contractions, the baby cannot descend through the pelvis. This can occur if the baby is in a breech position or the mother’s pelvis does not have the shape or size necessary for the baby to pass through (cephalopelvic disproportion). Approximately 8% of all women giving birth are affected by a prolonged labor; most often caused by heavy birthweight and/or a large head circumference.
There is debate however, on whether cephalopelvic disproportion (CPD) actually exists unless a woman previously had rickets or pelvic fractures, the baby has a condition that makes the head much larger, or a postterm baby whose head sutures (soft parts between the skull bones) have already begun to fuse.
Diagnosis of CPD is very difficult and usually relies on the experience of the HCP. No method has been definitively shown to accurately predict CPD prior to labor. However, the biggest risk from a misdiagnosis of CPD is an unnecessary cesarean section.
Prolonged labor can also be caused by the mother's exhaustion or difficulty pushing due to the use of an epidural. However, neither exhaustion nor epidural leads directly to assisted delivery (forceps/vacuum) or cesarean section if the baby is tolerating labor well. The mother should have time to rest and the epidural can be stopped (may take an hour or two to wear off).
Stress and/or fear can also prolong labor, but not all studies have reached this conclusion. Regardless, it is estimated that approximately 6% to 10% of women experience such an intense fear of labor and delivery that it may disrupt the labor process. While a certain amount of fear is considered healthy and can help women remain alert and energetic, extreme stress and fear does the opposite.
An unhealthy level of fear and anxiety results in an increase in hormones that overwhelms the hormones needed for labor. Oxytocin, the hormone required for contractions, is secreted from the pituitary gland/hypothalamus; however, the hypothalamus also releases hormones related to stress. Therefore, any extra stimuli from the hypothalamus may suppress the secretion of oxytocin.
Read here for more information on how stress hormones and/or fear may stall labor, or make labor pain worse.
Labor Augmentation
If labor is truly prolonged or protracted, HCPs can try several steps prior to moving forward with a cesarean delivery. Augmentation of labor is the process of stimulating the uterus to increase the frequency, duration and intensity of contractions. Labor can be augmented through oxytocin or amniotomy, as well as assisted delivery – the latter mostly due to maternal exhaustion.
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As a form of augmentation, oxytocin is used:
In labors that started on their own, but contractions have either slowed down or are not building in strength or intensity needed for labor to progress
If dilation rates are slower than expected
To prevent slow progress from occurring in the first place
Response to oxytocin is different in every woman and depends on preexisting uterine activity, cervical status, receptor status, pregnancy duration, and biological differences.
Early amniotomy is also a common method to speed up labor.
An amniotomy is the purposeful rupture of membranes by the HCP during labor. An amniotomy can be used to help speed up the progression of labor, usually after 4 cm of dilation, or at full dilation if the membranes have not yet ruptured. Only about 10% of women “break their water” prior to labor.
However, even when amniotomy is used as an augmentation method, active labor onset can still be unpredictable, and there is no guarantee that labor will "speed up" as a result.
Although technically not an augmentation method, assisted delivery (forceps/vacuum) can also be used.
ACOG has recommended physician training in forceps/vacuum use to reduce the rates of cesarean section, which is the main advantage of their use. Cesarean delivery is considered to have a higher risk of complications than assisted delivery methods. However, HCPs also need to be properly trained, and current obstetricians are trained more frequently in the use of vacuum assisted delivery over forceps.
An HCP may decide to use assisted delivery:
If there are concerns about the baby’s heart rate
The woman is tired, and the baby’s head has stopped moving through the birth canal (however, this is subjective and the woman should have time to rest if fetal assessment is reassuring)
A medical condition (such as heart disease) limits her ability to push
The baby’s position (head rotation only)
Cesarean section may be recommended if the HCP determines, that based on fetal signs (heart rate, movement, position), that immediate delivery is necessary.
Action
All women – no matter what their birth plan is – should be aware of the methods and options for augmentation of labor in the event they are recommended due to protracted or prolonged labor. This way, women have time to understand the process, the methods used, the risks and benefits of each, and have plenty of time to ask their HCP questions. They will also feel more confident in their decisions and have a better understanding of why certain options are used and when.
Women should also understand research behind dilation rates and strategies for pushing; this information – and through discussion with their HCP – can help women avoid unnecessary interventions during labor and delivery.
Resources
Safe Prevention of the Primary Cesarean Delivery (American College of Obstetricians and Gynecologists)
Abnormal Labor (StatPearls/NCBI)
Introduction - Labor Dystocia (StatPearls/NCBI)