Prevention of the primary caesarean section - nuances in success and safety
Following on from the ACOG/SMFM consensus guideline
The ACOG/SMFM obstetric care consensus was first published in 2014 and re-affirmed in 2016. I won’t summarise the recommendations, but you can read it here:
I’ve been keeping my eye out for any evidence-based validation or critique of the findings and, to date, have come across two interesting ones. The first is from Paris: a before/after retrospective cohort study over two consecutive, 1-year periods at a University hospital.
Thuillier C, Roy S, Peyronnet V, et al. Impact of recommended changes in labor management for prevention of the primary cesarean delivery. Am J Obstet Gynecol 2018;218:341.e1-9.
Some more about their results:
Intervention between the two periods: changes as per ACOG/SMFM consensus
Primary outcome: global caesarean delivery (CD) rate, secondary outcomes: CD rate for failed IOL, 1st/2nd stage arrest of labour (AoL), non-reassuring FHR, duration of labour, timing of CD, rates of operative deliveries, perineal lacerations & postpartum haemorrhage.
6531 women with vertex pregnancies at term and epidural analgesia, similar obstetric characteristics.
Overall CD rate: reduced from 9.4% to 6.9% (OR 0.71 - significant)
CD rate for AoL first stage: reduced from 1.8% to 0.9% (OR 0.51 - only significant for nulliparas)
CD rate for AoL second stage: no significant difference
CD rate for failed IOL: no significant difference
CD rate for non-reassuring FHR reduced from 5.6% to 4.3% (OR 0.75 - only significant for nulliparas)
Operative delivery rates fell from 19.5% to 17.2% (OR 0.85 - significant)
There was no apparent increase in immediate adverse maternal or neonatal outcome associated with this significant fall in primary CD rate.
A few things to note, however:
There was a significant increase in labour length before CD for active phase arrest of progress - median nulliparous labour length below in hours:
CD overall: pre-phase: 8h (4-11), post-phase: 10h (5-14)
CD for AoL first stage: 11h (9-14) vs 14h (12-16)
CD for AoL second stage (second stage length): 3h (2-4) vs 5h (4-6)
CD for failed IOL 10h (4-9) vs 15h (10-16)
Overall and first stage of labour lengths don’t seem unreasonably long - even at the higher end of the confidence intervals. Second stage of labour is concerning - an additional median 2 hours and confidence intervals ranging from 4 to 6 hours.
The Thuillier study didn’t include postpartum infectious morbidity due to the availability of only data from initial hospitalisation. They acknowledge that other research does find an increase in endometritis with prolonged second stage. It was reassuring that their PPH rates were similar and neonatal admission no more likely.
Second stage of labour: research since 2016
In 2020, Nelson et al, published a Clinical Opinion piece in AJOG about the second stage of labour length and the evidence since the ACOG/SMFM guidelines from 2014/2016.
They outline the evidence that a second stage of labour longer than 3 hours carries increased risk to the baby. The full paper above includes quantitative description of the findings below.
So what now?
I believe the Thuillier et al study gives us some reassurance about application of the ACOG/SMFM consensus to the first stage of labour for women who have an epidural. There were fewer caesareans after allowing longer labour time before calling arrest of progress, and it appears safe.
The second stage of labour is a different story. Despite a longer length of the second stage, there were no differences in CD rate - and Nelson et al clarify for us the potential harms of a second stage longer than 3 hours.
Any other studies using the consensus? In particular relating to the overall population - not just those who have epidural analgesia.
DT
