Is labor longer? Does it matter?

I’ve spent quite a few hours puzzling over an important new obstetric paper, and I’m still not sure what to make of it.

The paper is Changes in labor patterns over 50 years by Laughton, Branch, Beaver and Zhang; it was released online in advance of print publication. The authors assert that labor is longer now than it was 50 years ago, that obstetric interventions are to blame and that longer labor is a bad thing.

Specifically:

Data from pregnancies at term, in spontaneous labor, with cephalic, singleton fetuses were compared between the Collaborative Perinatal Project (CPP, n= 39,491 delivering 1959 – 1966) and the Consortium on Safe Labor (CSL, n=98,359 delivering 2002 – 2008).

Results

Compared to the CPP, women in the CSL were older (26.8 ± 6.0 versus 24.1 ± 6.0 years), heavier (BMI 29.9 ± 5.0 versus 26.3 ± 4.1 kg/m2), had higher epidural (55% versus 4%) and oxytocin use (31% versus 12%), and cesarean (12% versus 3%). First stage of labor in the CSL was longer by a median of 2.6 hours in nulliparas and 2.0 hours in multiparas, even after adjusting for maternal and pregnancy characteristics, suggesting that the prolonged labor is mostly due to changes in practice patterns.

Conclusions

Labor is longer in the modern obstetrical cohort. The benefit of extensive interventions needs further evaluation.

There is no doubt that the data demonstrate that labor is longer in the modern cohort of patients investigated by the authors, but it is not clear that interventions are responsible, or that this is a bad thing, given that neonatal outcomes were better in the modern cohort.

The authors compared two large datasets:

The course of labor and method of delivery were compared between the National Collaborative Perinatal Project (CPP) and the Consortium on Safe Labor (CSL). The National Collaborative Perinatal Project was a prospective study of approximately 54,000 births to 44,000 women recruited from 1959 to 1965 (last delivery in 1966)…

The Consortium on Safe Labor was a retrospective cohort study conducted by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health and included women giving birth between 2002 and 2008, with the majority (87%) between 2005 and 2007. There were 228,668 deliveries …

They restricted the analysis to women who started labor spontaneously and who went on to have a vaginal delivery.

They found that the maternal characteristics and intervention rates differed markedly between the two cohorts:

Compared to women in the CPP study, women in the CSL study were older (26.8 ± 6.0 versus 24.1 ± 6.0 years), had a higher average pre-pregnancy BMI (24.6 ± 5.6 versus 22.6 ± 4.2 kg/m2), had a higher average BMI at delivery (29.9 ± 5.0 versus 26.3 ± 4.1 kg/m2), and were more racially diverse (P <0.001 for all comparisons. Even though the women in the CSL study delivered on average 0.7 weeks (4.9 days) earlier, their neonates weighed on average 99 grams more. Epidural use and oxytocin augmentation were much more common in the CSL compared to the CPP (55% versus 4%, and 31% versus 12%, respectively), while operative vaginal delivery was less common during the CSL compared to the CPP (6% versus 40% ). Episiotomy was also far less common in the CSL, with 17% undergoing this procedure compared to 68% in the CPP. The intrapartum cesarean delivery rate was 4 times higher in the CSL compared to the CPP (12% versus 3%).

Data analysis of the first stage of labor showed:

The median time for first stage of labor increased significantly between the CPP and CSL for all parities, regardless of cervical dilation upon admission. In nulliparas, even though the median cervical dilation and effacement were slightly more favorable on admission, the median time for first stage of labor from 4 cm to completely dilated was 2.6 hours longer in the CSL. After adjusting for maternal age, race, BMI at delivery, gestational age at delivery, spontaneous rupture of membranes and birth weight, the median time for first stage of labor was still 2.6 hours longer. Both secundagravidas and multiparas had similar cervical dilation and slightly greater effacement upon admission in the CSL compared to the CPP From 5 cm to completely dilated, the median time for first stage of labor was 1.8 hours for secundagravidas (P1) and 1.7 hours for multiparas (P2+) in the CSL. After adjusting, these times were slightly longer (2.0 hours for both).

The authors looked at the second stage of labor, but felt they could not draw valid conclusions because the extensive use of forceps in the earlier cohort artificially shortened the second stage.

How about neonatal outcomes?

Neonates weighed more in the CSL: 113 g more for nulliparas, 117 g for secundagravidas (P1), and 93 g for multiparous women (P2+). Neonatal Apgar scores at 1 and 5 minutes were higher in the CSL compared to CPP, regardless of parity. After adjusting for maternal and obstetrical characteristics, there was still a lower percentage of Apgar scores < 7 at 5 minutes in the CSL compared to CPP for all parities (3-4% lower difference, P <0.001 for all).

The authors conclude:

Labor patterns differ in contemporary practice in the CSL compared to approximately 50 years ago in the CPP. The first and second stages of labor were longer in the CSL, with an overall slower latent phase, a less obvious inflection point in nulliparas, and a later inflection point in multiparas. After adjusting for the differences in maternal and pregnancy characteristics, labor was still significantly longer in the modern CSL cohort compared to the older CPP cohort… In nulliparous women, changes in obstetric practice appear to have contributed the most to the longer median first stage of labor (from 4 cm to 10 cm cervical dilation) in the modern CSL cohort compared to the older CPP cohort. In secundagravidas (P1) and multiparous women (P2+), changes in obstetric practice contributed to almost all of the difference to the longer median first stage of labor (from 5 cm to fully dilated).

Of note, the principal difference in labor patterns between the two groups appears to be a longer latent phase in the contemporary group. In other words, active labor now starts closer to 6cm instead of the classic active phase which began at 4 cm. Once active labor started, the length of the remaining labor was very similar.

As I said above, the data seems to clearly demonstrate that labor patterns have changed. However, the conclusion drawn by the authors, that obstetric interventions (specifically epidurals and oxytocin augmentation) are responsible for this change is only one possible explanation.

As the authors acknowledge, oxytocin use can only shorten labor, so it cannot be responsible for lengthening labor. Indeed the increased use of oxytocin may be the result of longer labors, not the cause. That leaves only (in the authors’ judgment) epidurals.

Could epidurals be the cause of longer labors? It’s certainly possible. What puzzles me, however, is that the authors could have analyzed their data to clarify the role of epidurals, but they chose not to do so. The authors could have compared labor patterns in women who did and did not have epidurals in each cohort. It’s a mystifying omission. Why conclude that epidurals are responsible when the data could be analyzed to demonstrate whether epidurals are or are not responsible?

Let’s assume for the moment that epidurals are leading to longer labors? Is that necessarily a bad thing?

The authors are quick to dismiss the substantial difference in Apgar scores between the two cohorts and don’t even bother to mention the substantial difference in perinatal mortality between the two cohorts (overall perinatal mortality in the early 1960’s was more than 3 times higher than in the early 2000’s). The authors plainly state their assumption that the bulk of the improvement in neonatal outcomes can be attributed to advances in neonatology. While that might hold true for mortality rates, it is difficult to see why credit for higher Apgar scores should be assigned to neonatologists when Apgar scores are often determined before neonatologists arrive on the scene.

The authors make much of the fact that longer labors contribute to higher healthcare costs:

…In 2010, Intermountain Healthcare obstetric facilities managed 5,439 vaginal births in nulliparous women entering into spontaneous labor. A conservative estimate of the nursing cost alone for labor care in the Intermountain Healthcare system is 46.00 per hour (an average cost derived from analysis of women in active labor). Thus in terms of the longer median time in labor for nulliparous women in the CSL study, the attributable cost is $110.40 per case, amounting to an annual cost of $600,466 within the Intermountain Healthcare system. The implications for healthcare systems and payors are obvious and should drive a reconsideration of modern-day labor process management with an eye towards process improvement.

I’m not sure why they are so excited by this since by definition, epidurals are going to increase the cost of labor. The catheters, anesthetics and involvement of an anesthesiologist increase costs whether labor is longer or not. What I find completely inexplicable is that the authors ignore the benefit of pain relief.

As is so often the case, women’s severe pain is completely ignored as if it is entirely meaningless. The pre-print version of the paper contains 29 pages and nowhere is those 29 pages do the authors acknowledge that a pain free labor is, for most women, the most important benefit of contemporary obstetric practice. Would anyone bemoan the fact that the immediate recovery from amputations is longer since the introduction of general anesthesia than it was in the “good old days” when they strapped the patient down and hacked off his limb as quickly as possible. No one seems to begrudge the additional cost of an anesthesiologist and all the anesthesiology equipment and medications used in performing an amputation. Yet, we are supposed to begrudge the cost of safe effective pain relief in labor, which is arguably more painful than an amputation.

Is labor longer with an epidural? Could be, but why is that a problem? Neonatal outcomes are far better, and women experience far less severe pain. Shouldn’t that be take home message from this study, and not dismay over longer labors?