By John C. Hobbins, MD

Professor, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora

Dr. Hobbins reports no financial relationships relevant to this field of study.

SYNOPSIS: A recent randomized clinical trial has shown that using a more liberal threshold for second stage labors in nulliparous patients with and without epidural can result in a major decrease in the need for cesarean sections.

SOURCE: Gimovsky AC, Berghella V. Randomized control trial of prolonged second stage: Extending the time limit vs usual guidelines. Am J Obstet Gynecol 2016;214:361.e1-6.

Despite the slight dropoff in cesarean section rate (CSR) from the record high of 32% in 2009, the National Institute of Child Health and Development (NICHD) and the American Congress of Obstetrics and Gynecology convened a workshop in 2012 to brainstorm ways to move the CSR downward toward the 20% rate that was attained in 1996. In its deliberations, the committee assessed various thresholds for the length of the second stage of labor, including the old dictum limiting the second stage length to two hours. The rationale for this was predicated on a 60-year-old study showing a significant increase in infant mortality when a two-hour second stage was exceeded. After reviewing more contemporary data, the committee concluded that longer second stage times should be allowed. These conclusions were then incorporated into a Society of Maternal Fetal Medicine (SMFM) Obstetric Care Consensus Report in 2014.1 In the SMFM report, “second stage arrest” meant prolongation by more than four hours in nulliparous women with epidurals or more than three hours in nullipara without epidurals. In multipara, this threshold was more than three hours with epidurals and more than two hours without them.

To prospectively test this approach further, a group from Philadelphia randomized nulliparous patients between 36/0 and 41/6 weeks who were undelivered after three hours of second stage with epidural or two hours without an epidural.2 One group had an immediate “expedited delivery” (by instrumental delivery or cesarean section) and the other group had an “extended labor” (another hour of trying).

Seventy-eight patients were randomized. The CSR in the extended group was 19.5% (8/41) and 43.2% in the expedited delivery group (16/37). This resulted in an odds ratio of 0.45 (95% confidence interval, 0.22-0.93). So for every four nulliparous women left to extend their second stages for another hour, one cesarean section would be averted. The differences in neonatal outcomes and maternal morbidities were the same in both groups.

COMMENTARY

For two decades, the two-hour limit on second-stage length was based on the 1952 study published by Hellman et al.3 In 13,000 patients, those authors found a 2.5-fold increase in infant death when the second stage exceeded two hours. In 1977, Cohen et al challenged the two-hour threshold by finding no difference in infant deaths in 4,400 deliveries when the two-hour limit was extended indefinitely.4 The difference between the two studies was that the later study included women who had continuous fetal heart rate (FHR) monitoring, which, theoretically, would detect impending fetal/neonatal demise. Also, most patients in the later study had epidurals. There was a small increase in low Apgar scores in patients whose second stage exceeded three hours, yet the authors concluded that there should be no preset limits on second stage length if there were no signs of hypoxia during FHR monitoring. ACOG then loosened its recommendation in 1989 to add one hour to the two-hour second stage threshold when epidurals were used.

The latest recommendations in the Obstetric Care Consensus report evolved from all of the data available to the committee prior to 2012.1 Soon after, the recommendations in that report were incorporated into many labor management protocols across the country.

The randomized, controlled trial in the March Gray Journal suggests that using these new permissive guidelines can decrease the CSR appreciably, which was the original goal of the NICHD workshop group.2 However, it doesn’t answer the safety question, since it was underpowered to show neonatal outcome, with only 41 and 37 patients in each study group.

The new guidelines have not been without detractors. In the April issue of the American Journal of Obstetrics and Gynecology, Levino and colleagues published a very provocative clinical opinion challenging the above recommendations.5 The authors focused on the inadequacies of the studies evaluated by the NICHD workshop group regarding safety. They pointed out that the effects of prolonged second stage were only assessed in neonates who were delivered vaginally. This excluded a group of infants who were delivered during the prolonged second stage by cesarean section because of non-reassuring FHR patterns, possibly ending in (unstudied) neonatal morbidity. As the authors stated, “how can we conclude that a second stage of greater than three hours is safe when all of the compromised infants delivered after three hours were excluded?” The authors in this Clinical Opinion piece then cited their own study from Parkland Hospital in Dallas consisting of data from 29,991 patients delivered between 2003 and 20086 and added more unpublished birth data on the same patients.5 They found that 5% delivered between three and four hours after full dilatation and 2% after four hours. However, most of the patients in these categories were waiting for a cesarean section or instrumental delivery to be done after earlier decisions had been made for intervention. Compared with nulliparas with less than three hour second stage, those with more than three hour second stages had significantly higher rates of five-minute Apgar scores < 4 (0.1% vs. 0.3%), seizures (0.1% vs. 0.8%), intubation at delivery (0.2% vs. 0.7%), neonatal ICU admissions (0.7 vs. 2.1%), and cord base deficits < 14 (1.1% vs. 2.3%). Although attaining statistical significance, the levels of these variables were still quite low and there were no neonatal deaths in the 1,489 prolonged second-stage patients.

Based on the presently shaky rationale for the various set-points for second stage lengths, my take is that the course of labor is extremely variable and it is difficult to set standards for a process that has so many outliers. There is no doubt that epidurals can lengthen labor, and with them nulliparous patients need to be given more time. The randomized, controlled trial above certainly suggests that a more permissive approach will decrease the CSR, but the Dallas data may lead to questions about the safety of this approach for some patients. However, rather than subject everyone to a rigid ceiling based on debatable evidence, there is still a place for flexibility while interjecting clinical acumen into the labor management equation.

REFERENCES

  1. American College of Obstetricians and Gynecologists; for Society of Maternal-Fetal Medicine. Safe prevention of primary cesarean delivery. Obstet Gynecol 2014; 123:693-711.
  2. Gimovsky AC, Berghella V. Randomized control trial of prolonged second stage: Extending the time limit vs usual guidelines. Am J Obstet Gynecol 2016;214:361.e1-6.
  3. Hellman LM, Prystowsky H. The duration of the second stage of labor. Am J Obstet Gynecol 1952;63:1223-1233.
  4. Cohen WR. The influence of the duration of second stage of labor on perinatal outcome and puerperal morbidity. Obstet Gynecol 1977;49:266-269.
  5. Leveno KJ, Nelson DB, McIntire DD. Second stage labor: How long is too long? Am J Obstet Gynecol 2016;214:484-489.
  6. Bleich AT, Alexander JM, McIntire DD, et al. An analysis of second stage labor beyond 3 hours in nulliparous women. Am J Perinatol 2012;29:717-722.