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Is there an upper time limit for the management of the second stage of labor?

      The epidemiology of the length of labor was notoriously reported by Emmanuel Friedman
      • Friedman E.A.
      The graphic analysis of labor.
      • Friedman E.A.
      Primigravid labor: a graphicostatistical analysis.
      in several landmark articles >50 years ago. These studies changed modern obstetrics; most specifically, they led to specific normative guidelines on the length of the first and second stages of labor. These normative guidelines generally have become prescriptive and have led to operative deliveries if the length of labor crosses some specific time threshold. However, more recently, a variety of authors have challenged this paradigm for both the first and second stages of labor. This seems reasonable, given that. although basic human biology has not likely changed since Friedman's studies, the management of labor has, most notably with the widespread use of epidural analgesia.
      See related articles, pages 357 and 361
      With regard to the first stage of labor, although several authors have concluded that the labor norms that were described by Friedman may not fit many current obstetric populations,
      • Albers L.L.
      The duration of labor in healthy women.
      • Zhang J.
      • Troendle J.F.
      • Yancey M.K.
      Reassessing the labor curve in nulliparous women.
      the standard curve still is used widely to guide labor interventions. For example, in a 1999 Albers
      • Albers L.L.
      The duration of labor in healthy women.
      found, in a descriptive study of spontaneous, term, vertex labor in women without epidural analgesia, that both nulliparous and multiparous women experienced labors that were considerably longer than those described in Friedman's studies. Similarly, Kilpatrick and Laros
      • Kilpatrick S.J.
      • Laros R.K.
      Characteristics of normal labor.
      and Zhang et al
      • Zhang J.
      • Troendle J.F.
      • Yancey M.K.
      Reassessing the labor curve in nulliparous women.
      also found lengths of spontaneous labor to be longer than those described in Friedman's cohort. Again, although changes in obstetric management may be responsible for some of these differences, demographic changes of the obstetric population may also be somewhat responsible because there have been differences in the length of labor that have been demonstrated by race/ethnicity
      • Greenberg M.B.
      • Cheng Y.W.
      • Hopkins L.M.
      • Stotland N.E.
      • Bryant A.S.
      • Caughey A.B.
      Are there ethnic differences in the length of labor?.
      and maternal age.
      • Greenberg M.B.
      • Cheng Y.W.
      • Sullivan M.
      • Norton M.E.
      • Hopkins L.M.
      • Caughey A.B.
      Does the length of labor vary by maternal age?.
      These differences would not matter particularly if clinicians were not using the norms that were defined by Friedman
      • Friedman E.A.
      The graphic analysis of labor.
      • Friedman E.A.
      Primigravid labor: a graphicostatistical analysis.
      to guide practice. However, 1 of the most common indications for a cesarean delivery is active phase arrest, which is established commonly as no progress in the active phase of labor for 2 hours, despite adequate uterine contractions. However, Rouse et al
      • Rouse D.J.
      • Owen J.
      • Savage K.G.
      • Hauth J.C.
      Active phase arrest: revisiting the 2 hour minimum.
      demonstrated that, by simply extending the time interval from 2-4 hours, >50% of women in spontaneous labor would proceed to a vaginal delivery. Further, in a recent study by Henry et al,
      • Henry D.M.
      • Cheng Y.W.
      • Shaffer B.L.
      • Kaimal A.J.
      • Bianco K.
      • Caughey A.B.
      Perinatal outcomes in active phase arrest and vaginal delivery.
      it was demonstrated that the women who went on to achieve a vaginal delivery after an active phase arrest diagnosis also had better maternal outcomes because of less infectious and bleeding morbidity with no difference demonstrated in neonatal outcomes.
      With regard to the second stage of labor, again Friedman's studies
      • Friedman E.A.
      The graphic analysis of labor.
      • Friedman E.A.
      Primigravid labor: a graphicostatistical analysis.
      have provided the standard thresholds that have been used, often with hour modifications added for epidural use. However, more recent studies have been in disagreement with the norms that were described by Friedman. For example, the women studied by Albers
      • Albers L.L.
      The duration of labor in healthy women.
      had lengths twice as long as those described by Friedman for both nulliparous (54 min vs 33 min) and multiparous (18 min vs 9 min) women; similar to Friedman's study, the women in this study did not have epidural analgesia.
      • Albers L.L.
      The duration of labor in healthy women.
      In the setting of epidural use, the second stage has been described as lasting even longer.
      • Greenberg M.B.
      • Cheng Y.W.
      • Hopkins L.M.
      • Stotland N.E.
      • Bryant A.S.
      • Caughey A.B.
      Are there ethnic differences in the length of labor?.
      • Greenberg M.B.
      • Cheng Y.W.
      • Sullivan M.
      • Norton M.E.
      • Hopkins L.M.
      • Caughey A.B.
      Does the length of labor vary by maternal age?.
      As of 2000, the American College of Obstetricians and Gynecologists (ACOG) defined a prolonged second stage of labor in nulliparous women as the lack of continuing progress for 3 hours with regional anesthesia or 2 hours without regional anesthesia; prolonged second stage of labor in multiparous women was defined as the lack of progress for 2 hours with or 1 hour without regional anesthesia.
      American College of Obstetricians and Gynecologists
      Operative vaginal delivery: ACOG practice bulletin no. 17.
      To be clear, however, these guidelines are not based on prospective, randomized trials. Fundamentally, the ideal management of the second stage should maximize the probability of vaginal delivery while minimizing the risks of maternal and neonatal morbidity and death. It appears that, with intensive intrapartum surveillance, timely identification of fetuses who are intolerant of labor can occur and actions subsequently can be taken to avoid fetal asphyxia.
      American College of Obstetricians and Gynecologists
      Operative vaginal delivery: ACOG practice bulletin no. 17.
      Thus, ACOG has advised that “the length of the second stage of labor is not in itself an absolute or even strong indication for operative termination of labor.”
      American College of Obstetricians and Gynecologists
      Operative vaginal delivery: ACOG practice bulletin no. 17.
      In the current edition of the American Journal of Obstetrics and Gynecology, 2 articles add further information to guide management decisions regarding the second stage of labor with slightly different conclusions to guide the clinician. Both studies are secondary analyses of prospectively collected data from randomized, controlled trials. In the study by Rouse et al,
      • Rouse D.J.
      • Weiner S.J.
      • Bloom S.L.
      • et al.
      Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes.
      which was based on data collected in the study of the fetal pulse oximeter, the study demonstrated no difference in neonatal outcomes, although several maternal outcomes (eg, chorioamnionitis, 3rd- and 4th-degree perineal lacerations, and uterine atony) were reported to have increased with a longer second stage. The study by LeRay et al,
      • Le Ray C.
      • Audibert F.
      • Goffinet F.
      • Fraser W.
      When to stop pushing: effects of duration of second-stage expulsion efforts on maternal and neonatal outcomes in nulliparous women with epidural analgesia.
      which is an analysis of data from a randomized clinical trial of passive descent, also reported a higher rate of chorioamnionitis, even after the data were controlled for potential confounders.
      Because these studies are observational with respect to the length of the second stage and the outcomes reported, one must consider whether the relationship between length of second stage and chorioamnionitis is causal. I would propose that, although it seems that a certain percentage of the increase in chorioamnionitis may be due to the frequent examinations in the second stage and the longer exposure to ruptured membranes, it may also be that women in whom chorioamnionitis was developing would, in turn, be more likely to demonstrate a dysfunctional labor pattern, weaker uterine contractions, and, thus, experience a prolonged second stage of labor. This reverse causality therefore would not be prevented necessarily by earlier intervention in the second stage.
      In addition to the unadjusted findings from these studies, the finding of uterine atony and findings from other studies of the second stage that demonstrate more maternal hemorrhage
      • Cheng Y.W.
      • Hopkins L.M.
      • Caughey A.B.
      How long is too long: is a prolonged second stage of labor associated with worse maternal and neonatal outcomes?.
      • Allen V.M.
      • Baskett T.F.
      • O'Connell C.M.
      • McKeen D.
      • Allen A.C.
      Maternal and perinatal outcomes with increasing duration of the second stage of labor.
      • Lu M.C.
      • Muthengi E.
      • Wakeel F.
      • Fridman M.
      • Korst L.M.
      • Gregory K.D.
      Prolonged second stage of labor and postpartum hemorrhage.
      should also undergo consideration of causality. It may be that women who are predisposed to a longer second stage of labor because of dysfunctional labor or decreased uterine contractility are also more likely to have uterine atony and postpartum hemorrhage. Essentially, it may be that the prolonged labor and postpartum hemorrhage are both a product of a common cause, as opposed to the latter being caused by the former.
      The other outcome that may not be related causally to a prolonged labor in a biologic sense is the 3rd- or 4th-degree perineal laceration rate. In fact, it is likely that the obstetric intervention of an operative vaginal delivery at 2, 3, or whatever arbitrarily defined threshold may increase such outcomes as perineal lacerations, obstetric hemorrhage, and shoulder dystocia. Thus, it is likely that the finding in the study of LeRay et al,
      • Le Ray C.
      • Audibert F.
      • Goffinet F.
      • Fraser W.
      When to stop pushing: effects of duration of second-stage expulsion efforts on maternal and neonatal outcomes in nulliparous women with epidural analgesia.
      that the chances of a spontaneous vaginal delivery falls to <10% beyond 3 hours of the second stage is related to obstetric intervention and an overall rate of operative vaginal delivery of 40% in their study. This calls into question their conclusion that consideration should be given to even earlier intervention. Certainly, this is not supported by the findings of Rouse et al,
      • Rouse D.J.
      • Weiner S.J.
      • Bloom S.L.
      • et al.
      Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes.
      who agree with the ACOG conclusions regarding the lack of evidence to support an absolute time threshold to end the second stage with intervention.
      Thus, as with many of the most intriguing studies, these 2 articles inspire more research questions and encourage the design of specific studies to determine whether we can improve outcomes in the second stage. First, even these prospective studies, as with Friedman's,
      • Friedman E.A.
      The graphic analysis of labor.
      • Friedman E.A.
      Primigravid labor: a graphicostatistical analysis.
      do not truly address the epidemiologic function of the second stage of labor. Because of intervention with operative vaginal delivery, it is unclear what the chance of actually progressing to a spontaneous vaginal delivery is as the second stage progresses. Given this, the findings from these 2 studies and others
      • Myles T.D.
      • Santolaya J.
      Maternal and neonatal outcomes in patients with a prolonged second stage of labor.
      that the neonatal outcomes do not appear to worsen with a longer second stage and that intervention with an operative vaginal delivery does likely worsen maternal outcomes, the stage is set to conduct a prospective, randomized, controlled trial of operative vaginal delivery in nulliparous women at 2 or 3 hours of the second stage vs expectant management. Only with such a study can the question of which management leads to better outcomes be truly answered.
      Given that 1 of the most common indications for an operative vaginal delivery is a prolonged second stage of labor, it seems worthy of study. Such a study should not only examine the short-term outcomes of maternal infectious morbidity, hemorrhage, and perineal lacerations but also should investigate the potential effect of operative vaginal delivery vs expectant management on urogynecologic outcomes. Until such a time that such an interventional study is completed, the recommendations from ACOG appear to be supported by the existing literature. Thus, although as obstetricians many of us have been trained to consider a prolonged second stage to be an indication for operative delivery, we must maintain a careful awareness of the benefits and risks of intervention vs continued expectant management of the second stage.

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