The month of May is devoted normative information from a 2014 “Obstetric Care Consensus” project by ACOG & Society for Maternal-Fetal Medicine (SMFM).
Today’s topic is the length of 1st stage labor (from an obstetrical perspective).
Abstract:
http://www.acog.org/Resources-And-Publications/Obstetric-Care-Consensus-Series/Safe-Prevention-of-the-Primary-Cesarean-Delivery
This document was developed jointly by the American College of Obstetricians and Gynecologists (the College) and the Society for Maternal-Fetal Medicine with the assistance of Aaron B. Caughey, MD, PhD; Alison G. Cahill, MD, MSCI; Jeanne-Marie Guise, MD, MPH; and Dwight J. Rouse, MD, MSPH. The information reflects emerging clinical and scientific advances as of the date issued, is subject to change, and should not be construed as dictating an exclusive course of treatment or procedure. Variations in practice may be warranted based on the needs of the individual patient, resources, and limitations unique to the institution or type of practice.
In 2011, one in three women who gave birth in the United States did so by cesarean delivery. Cesarean birth can be life-saving for the fetus, the mother, or both in certain cases. However, the rapid increase in cesarean birth rates from 1996 to 2011 without clear evidence of concomitant decreases in maternal or neonatal morbidity or mortality raises significant concern that cesarean delivery is overused. Variation in the rates of nulliparous, term, singleton, vertex cesarean births also indicates that clinical practice patterns affect the number of cesarean births performed.
The most common indications for primary cesarean delivery include, in order of frequency, labor dystocia, abnormal or indeterminate (formerly, nonreassuring) fetal heart rate tracing, fetal malpresentation, multiple gestation, and suspected fetal macrosomia. Safe reduction of the rate of primary cesarean deliveries will require different approaches for each of these, as well as other, indications. For example, 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 was historically taught.
Additionally, improved and standardized fetal heart rate interpretation and management may have an effect. Increasing women’s access to nonmedical interventions during labor, such as continuous labor and delivery support, also has been shown to reduce cesarean birth rates. External cephalic version for breech presentation and a trial of labor for women with twin gestations when the first twin is in cephalic presentation are other of several examples of interventions that can contribute to the safe lowering of the primary cesarean delivery rate.
Balancing Risks and Benefits
Childbirth by its very nature carries potential risks for the woman and her baby, regardless of the route of delivery. The National Institutes of Health has commissioned evidence-based reports over recent years to examine the risks and benefits of cesarean and vaginal delivery (3) (Table 1). For certain clinical conditions––such as placenta previa or uterine rupture––cesarean delivery is firmly established as the safest route of delivery. However, for most pregnancies, which are low-risk, cesarean delivery appears to pose
However, for most pregnancies, which are low-risk, cesarean delivery appears to pose a greater risk of maternal morbidity and mortality than vaginal delivery (4) (Table 1).
- What is the appropriate definition of abnormally progressing first-stage labor?
Definition of Abnormal First-Stage Labor
The first stage of labor has been historically divided into the latent phase and the active phase based on the work by Friedman in the 1950s and beyond. The latent phase of labor is defined as beginning with maternal perception of regular contractions (17). On the basis of the 95th percentile threshold, historically, the latent phase has been defined as prolonged when it exceeds 20 hours in nulliparous women and 14 hours in multiparous women (18). The active phase of labor has been defined as the point at which the rate of change of cervical dilation significantly increases.
Active phase labor abnormalities can be categorized either as protraction disorders (slower progress than normal) or arrest disorders (complete cessation of progress). Based on Friedman’s work, the traditional definition of a protracted active phase (based on the 95th percentile) has been cervical dilatation in the active phase of less than 1.2 cm/h for nulliparous women and less than 1.5 cm/h for multiparous women (19). Active phase arrest traditionally has been defined as the absence of cervical change for 2 hours or more in the presence of adequate uterine contractions and cervical dilation of at least 4 cm.
However, more recent data from the Consortium on Safe Labor have been used to revise the definition of contemporary normal labor progress (20). In this retrospective study conducted at 19 U.S. hospitals, the duration of labor was analyzed in 62,415 parturient women, each of whom delivered a singleton vertex fetus vaginally and had a normal perinatal outcome. In this study, the 95th percentile rate of active phase dilation was substantially slower than the standard rate derived from Friedman’s work, varying from 0.5 cm/h to 0.7 cm/h for nulliparous women and from 0.5 cm/h to 1.3 cm/h for multiparous women (the ranges reflect that at more advanced dilation, labor proceeded more quickly) (Table 2).
The Consortium on Safe Labor data highlight two important features of contemporary labor progress (Fig. 4). First, from 4–6 cm, nulliparous and multiparous women dilated at essentially the same rate, and more slowly than historically described. Beyond 6 cm, multiparous women dilated more rapidly. Second, the maximal slope in the rate of change of cervical dilation over time (ie, the active phase) often did not start until at least 6 cm. The Consortium on Safe Labor data do not directly address an optimal duration for the diagnosis of active phase protraction or labor arrest, but do suggest that neither should be diagnosed before 6 cm of dilation. Because they are contemporary and robust, it seems that the Consortium on Safe Labor data, rather than the standards proposed by Friedman, should inform evidence-based labor management.
