Condition

Approximately 80 percent of American women will eventually have at least one child,¹ and the majority of these women will undergo labor. “Labor dystocia” (difficult or obstructed labor)² encompasses a variety of concepts, ranging from “abnormally” slow dilation of the cervix or descent of the fetus during active labor³ to entrapment of the fetal shoulders after delivery of the head (“shoulder dystocia,” an obstetric emergency). For the purposes of this systematic review, we assume that “labor dystocia” refers to “abnormal” labor progression during the latent (up to 4-6 cm dilation) or active phases (from 4-6 cm until full dilation) of the first stage of labor, or during the second stage (from complete cervical dilation until delivery of the baby), although, as discussed below, there have been substantial changes in practice since these “traditional” definitions were developed which raise questions about their generalizability to modern populations. We also limit our review to women in spontaneous labor, with definitions varying somewhat between studies but generally including the onset of spontaneous uterine contractions, and explicitly exclude studies of women undergoing induction, or women with premature rupture of membranes at term in the absence of contractions.

Prolonged labor may increase the risk for maternal and neonatal infection, fetal distress, neonatal hypoxia, uterine rupture, and postpartum hemorrhage; it may also be a marker for increased risk of maternal pelvic floor and genital trauma during delivery (with a subsequent increased risk for future incontinence and pelvic organ prolapse).⁴ Reducing the likelihood of these adverse maternal and neonatal outcomes is the underlying rationale for performing a cesarean delivery for the primary indication of labor dystocia. ³

However, there is a tradeoff, since cesarean delivery itself increases the risk of maternal hemorrhage, venous thromboembolism, and injury to the bladder and other internal organs, and can affect post-delivery mother–baby interactions.^3,5 Further, having one cesarean delivery increases the likelihood of having subsequent cesarean deliveries.³ A woman’s risk for abnormal placentation (placenta previa or accreta, each of which is associated with significant maternal and neonatal morbidity and mortality) is directly related to the number of prior cesarean deliveries she has had.⁶

Although there is no consensus on the “optimal” cesarean delivery rate (conceptually, the rate that strikes a balance between benefits and harms for both mother and baby that is considered acceptable to most patients), there is general consensus that current rates in the United States are too high,^3,7 although whether the factors driving this rate are amenable to evidence-based solutions has been questioned.⁸ There is also growing concern about increases in rates internationally, as reflected by a World Health Organization consensus statement.⁹ Strategies to prevent a woman’s first, or primary, caesarean delivery may therefore lead to significant improvements in maternal and neonatal outcomes by reducing both the number of primary and repeat cesareans.³ For this reason, the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) have issued a joint consensus statement aimed at “preventing the first cesarean delivery,”³ with similar efforts instituted by the American College of Nurse Midwives.¹⁰ Since abnormalities of labor progression are the single most common cause of primary cesarean delivery in the United States,^3,11 strategies aimed at reducing cesarean delivery for dystocia may have the largest potential impact on overall cesarean rates.

Uncertainty about optimal management of dystocia may play a major role in the well-documented variation in cesarean delivery rates between hospitals that does not appear to be completely attributable to patient characteristics¹² (although other factors not directly related to evidence on comparative effectiveness, such as patient and provider preferences, real or perceived malpractice concerns, and local practice norms may also be important factors). Another source of uncertainty is that there are complex tradeoffs between patient preferences for the labor and delivery process, on the one hand, and outcomes on the other. These considerations involve issues related to setting (home, birthing center, hospital), provider (lay midwife, nurse-midwife, family physician, obstetrician), and available technology (including analgesia, fetal heart rate monitoring, and measurement of intrauterine pressure).^13–15 There is also wide variety in the maternal and neonatal outcomes that are reported, and the degree to which patient preferences for both process and outcomes is considered.^15–17

Diagnosis

The effective management of labor dystocia is first dependent on the tool used to diagnose the disorder. In the 1950s, Friedman published his observations on the rate of cervical change among a cohort of women in spontaneous labor¹⁸ and from this constructed labor curves representing the expected rate of cervical change in a population. Deviations from these curves, particularly rates of cervical change slower than expected from the Friedman curve are referred to as protracted or arrest disorders and represent labor dystocia. The Friedman curve has been the primary tool used to diagnose abnormal labor since then, though more recent data from the Consortium on Safe Labor have demonstrated that rates and characteristics of cervical change seen in modern obstetrics are quite different from that represented by the Friedman curve.¹⁹ Identifying what constitutes normal labor is an important initial step in the management of labor dystocia as it first dictates when various treatment options are initiated. Variation between providers about definitions or perceptions of “abnormal” labor length may contribute to variations in rates of diagnosis.

Prevention and Treatment Strategies

There are a number of strategies that may either facilitate earlier diagnosis of labor, directly or indirectly (e.g., choice of pain management strategies) prevent a diagnosis of labor dystocia, or accelerate labor progress after a diagnosis of dystocia. Strategies addressed in this report include:

• Use of graphs of cervical dilation versus time (“partograms”) to identify patients with slow labor progress, often with an indicator of when intervention is appropriate.
• Timing of the artificial rupture of the amniotic membranes (amniotomy) during labor.
• Various options for maternal positioning, ambulation, and feeding during labor.
• Use of epidural analgesia, or, alternatively, variations in technique (timing, choice of analgesic agents).
• Variations in monitoring labor progress (such as frequency of cervical examination or use of intrauterine pressure catheters) and fetal well-being (fetal heart rate monitoring).
• Variations in strategies for how oxytocin is used during labor augmentation including timing of augmentation relative to labor progress and variation in dosing regimens used.
• Variations in strategies for reducing the length of the second stage of labor (after cervical dilation is complete but before the baby has delivered), including different approaches to maternal pushing.

The overall goal of treating labor dystocia is to optimize delivery outcomes for mother and child, while attempting to achieve an optimal cesarean delivery rate. As discussed above, the optimal cesarean delivery rate is not known but is the lowest rate that balances benefits and harms to mother and child.

Scope of the Review

The present review evaluates the comparative effectiveness of different strategies for treating labor dystocia in women with otherwise uncomplicated pregnancies. We also limit our review to women in spontaneous labor and exclude those who are undergoing induced labor. In addition, one potential source of uncertainty in the available evidence may be variability in the definitions for different phases of labor, and what constitutes “normal” labor across studies and likely in practice as well. The definition of “normal” may vary across different populations and may depend on whether “normality” is based on a specified quantile of the distribution of rates of cervical change in the first stage of labor or rate of fetal descent in the second stage of labor, or on maternal and neonatal outcomes.^20–22 The statistical approach used to define “normality,” primarily in reference to rates of cervical change, has also been the source of controversy.^23–25 In order to better understand the impact of this variability on the evidence on specific interventions, we also review the evidence on the definition of “normal” labor progression.

We explicitly excluded studies which included women with other potential indications for cesarean section (e.g., multiple pregnancies, prior cesarean) or other conditions which might affect either the likelihood of diagnosis of dystocia (e.g., use of magnesium sulfate in preeclampsia) or lead to contraindications to some interventions (e.g., HIV and amniotomy). We also did not include interventions such as estimation of fetal size or clinical pelvimetry which might affect physician perception of the risk of labor dystocia.

Note that many studies evaluated interventions in nulliparous (women who have not previously given birth) and parous women (women who have previously borne one or more children) separately. Other studies did not indicate the women’s parity and were considered to be mixed parity or unspecified parity defined as potentially including both nulliparous and parous women.

Key Questions

The specific Key Questions (KQs) addressed in this review are listed below, and Figure 1 displays the analytic framework that guided our work.

• KQ 1: Do delivery outcomes for management of abnormal labor differ based on the criteria used to define protracted or arrested labor at different stages of the labor process?
• KQ 2: What are the benefits and harms of amniotomy in women in spontaneous labor?
• KQ 3: What are the benefits and harms of supportive care measures, including emotional support, ambulation, nutrition, and hydration, during spontaneous labor?
• KQ 4: What are the benefits and harms of epidural analgesia in labor, particularly in terms of the risk of a diagnosis of prolonged labor?
• KQ 5: How does the frequency of cervical examination affect the probability of specific benefits and harms?
• KQ 6: What are the benefits and harms of intrauterine pressure catheters in the diagnosis and management of labor dystocia?
• KQ 7: For women with abnormal labor, what are the relative benefits and harms of high- versus low-dose oxytocin protocols (including nipple stimulation)?
• KQ 8: For women in spontaneous labor undergoing augmentation with oxytocin, what are the relative benefits and harms (in terms of both maternal and neonatal outcomes) of electronic fetal monitoring versus intermittent auscultation?
• KQ 9: For women in the second stage of labor, is there a benefit from delayed or Valsalva pushing for time to delivery or mode of delivery?

Figure 1 depicts the KQs within the context of the populations, interventions, comparators, outcomes, timings, and settings (PICOTS) considered in this review. It illustrates the progression of spontaneous labor, which may be affected by interventions or management strategies performed prior to the diagnosis of abnormal progression; the criteria used to diagnose abnormal progression; and interventions performed after the diagnosis of abnormal progression.

Figure 1

Analytic framework. Abbreviations: AEs=adverse effects; KQ=Key Question; NICU=neonatal intensive care unit