New Labor Guidance, Part 2

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Welcome back! Last time, we talked the new Clinical Practice Guideline #8 and the first stage of labor. While there were some new things, many of the recommendations were unchanged.

Today we’re going to talk second stage – time from complete dilation to fetal delivery. There are some big differences here versus the previous Obstetric Care Consensus, and we’ll try to point them out as we go!

What is a normal length of second stage?

  • ACOG defines a prolonged second stage as:

    • Three hours or more in nulliparas

    • Two hours or more in multiparas

      • Furthermore, they recommend an individualized approach to diagnose second stage arrest, “incorporating factors regarding progress, clinical factors that may affect the likelihood of vaginal delivery, discussion of risks and benefits of available interventions, and individual patient preference” if planning to extend beyond these parameters.

      • Additionally, ACOG states that “second stage arrest can be diagnosed earlier if there is lack of fetal rotation or descent despite adequate contractions, pushing efforts, and time.”

  • This is a more open, individualized, and less time-focused than the prior “4/3/3/2” recommendations in the Obstetric Care Consensus.

    • The OCC also stated that there was no maximum amount of time in the second stage identified.

    • The recommendation to consider diagnosis prior to reaching these time points is based on some concerns that developed in the literature that providers were failing to recognize issues in the second stage altogether by focusing on the “4/3/3/2” time, and that the “4/3/3/2” recommendations were not based in evidence supporting safety.

      • CPG 8 takes an attempt at establishing some evidence:

        • Observational study of over 53,000 laboring patients:

          • Probability of vaginal delivery decreased with prolonged pushing time, but:

            • At 4 hours, chance of vaginal delivery in nullipara remained 78%

            • At 2 hours, chance of vaginal delivery in multipara remained 81%

          • Longer pushing duration resulted in statistically significant rise in composite neonatal morbidity

            • However, the absolute risk difference was small – less than 1%.

            • Other studies have been mixed about neonatal outcomes with respect to prolonged second stage.

          • Longer pushing duration resulted in rise in maternal risk:

            • 3rd/4th degree laceration

            • Operative vaginal delivery

            • Postpartum hemorrhage

            • Cesarean delivery

    • If you remember the Obstetric Care Consensus, you might remember that the “additional hour of pushing time” was allotted for patients who had epidurals. Is that the same?

      • They do note in the text that, based on Consortium for Safe Labor data, second stage was prolonged by about one additional hour in patients with an epidural.

        • The additional clinical factors to consider include things like position (i.e., OP), maternal BMI, fetal weight, and the fetal station at time of complete dilation.

      • However, studies performed since then demonstrated that, while prolonging the second stage by an additional hour resulted in more vaginal deliveries, it also increased risk of neonatal acidemia, NICU admission, and 3rd/4th degree lacerations.

        • Thus, individualized discussions and management are highly encouraged. Keep the following in mind:

          • Ongoing management of the second stage presumes continued demonstration of fetal descent. The limits written are total expected times for second stage – so if you’re not seeing anything, that’s cause for concern.

          • 95% of patients are at 0 station or lower (on -5 to +5 scale) at complete dilation – so if patients are higher than this, that is also concerning.

How do I manage a prolonged second stage?

  • Pushing timing

    • ACOG recommends commencing pushing when complete cervical dilation is achieved.

      • ACOG discusses the controversy surrounding “delayed pushing” or “passive descent” in this document, raising the findings of a recent high-profile RCT as well as a meta-analysis of 12 trials on the subject.

        • The arguments go that delayed pushing minimizes patient exertion with pushing efforts, while immediate pushing more closely mimics the physiology of unanesthetized patients, whose pain makes them push earlier.

      • Among high-quality studies, delayed pushing does not improve vaginal delivery rates.

      • Additionally, delayed pushing prolongs time in labor; and in the high-profile RCT, the study was stopped early because of increased rates of chorioamnionitis, postpartum hemorrhage, and neonatal acidemia in the delayed pushing arm.

        • So get to pushing!

  • Manual rotation

    • Positions such as OT or OP can be difficult to achieve vaginal delivery due to the mechanics of the fetal head within the pelvis.

      • Using a hand to rotate the head into an OA position has been demonstrated in observational studies to be successful about 70% of the time, while reducing cesarean and operative delivery rates, and not causing infant harm.

        • However, an RCT comparing a sham rotation to true rotation did not demonstrate any benefit, but was not powered to determine any risk of harm.

      • Knowing position of the fetal spine may help influence success, as has been demonstrated in one RCT – so don’t be afraid to have an ultrasound to 1) confirm position before rotation, and 2) help know which way to rotate!

    • Timing of manual rotation has not been adequately studied, so it can be performed at any point in the second stage.

  • Operative delivery

    • ACOG suggests an assessment for operative vaginal delivery before performing cesarean for second stage arrest.

      • Outcome comparisons of operative vaginal delivery and unplanned cesarean delivery demonstrate reduced maternal morbidity after successful operative delivery, with similar rates of serious neonatal morbidity.

        • This is no surprise to our listeners who have tuned in to our operative vaginal delivery podcast!

          • Check out that podcast for more details – but the rates of intracranial hemorrhage are similar for second stage cesarean and vacuum delivery, and failure rates are low – under 3% for low or outlet procedures.

      • That said, operative delivery requires special skill and training, which is becoming less frequent. Cesarean is still the “safety backstop” when these cannot be performed or if a patient declines operative delivery.

        • Be prepared for higher rates of endometritis and for more significant bleeding and hysterotomy extensions. 

        • Listen to our recent podcast on difficult fetal extractions, too, as you’ll encounter this more frequently with second stage cesarean.