The 20 minute electronic fetal monitoring strip is a “right of passage” for any woman being admitted to the hospital in labor. But is this automatic 20 minute strip evidence based? Regular Science & Sensibility contributor Henci Goer takes a look at a recent Cochrane systematic review and lets us know what the research says. Do you discuss this with your students? Do you share about this practice in your classes and with your patients and students? What do you tell them? Will it change after reading Henci’s review below? – Sharon Muza, Science & Sensibility Community Manager
Some weeks ago, I did a Science and Sensibility post summarizing the latest version of the Cochrane systematic review of continuous electronic fetal monitoring (EFM)—AKA cardiotocography (CTG)—in labor versus intermittent listening. A couple of commenters on that post asked if I would tackle the “admission strip,” the common practice of doing EFM for 20 minutes or so at hospital admission in labor to see whether ongoing continuous monitoring is warranted.
I was in luck because the Cochrane Library has a recent systematic review of randomized controlled trials of this practice versus intermittent listening in women at low risk for fetal hypoxia (Devane 2012). The rationale for the admission strip, as the reviewers explain, is that pregnancy risk factors don’t predict all babies who will experience morbidity or mortality in labor. The admission strip is an attempt to identify women free of risk factors whose babies nevertheless might benefit from closer monitoring. Let’s see whether the admission strip succeeds at identifying those babies and improving their outcomes.
As to whether the admission strip identifies babies believed to be in need of closer surveillance, the answer is “yes.” Pooled analysis (meta-analysis) of the trials found that 15 more women per 100 allocated to the admission strip group went on to have continuous EFM (3 trials, 10,753 women), and 3 more babies per 100 underwent fetal blood sampling (3 trials, 10,757 babies).
Furthermore, women almost certainly underwent more cesareans as well (4 trials, 11,338 women). All four trials reported more cesareans in the admission strip group. The pooled increased risk of 20% just missed achieving statistical significance, but this is probably because cesarean rates were so low, only 3 to 4% in by far the biggest trial, which contributed 8056 participants. Because of the lack of heterogeneity among trials, the reviewers think the difference is likely to be real. If it is, then using an admission strip in low-risk women results in 1 additional cesarean for every 136 women monitored continuously (number needed to harm). I would add that not separating out first-time mothers, who are at greater risk for cesarean delivery, probably masked a bigger effect in this subgroup. How big an effect might this be? Let’s assume a 9% cesarean rate in low-risk first-time mothers, that being the rate found in first-time mothers still eligible for home birth at labor onset in the Birthplace in England study (2011). At this cesarean rate, a 20% increase over baseline would calculate to 1 additional cesarean for every 55 first-time mothers monitored continuously.
The crucial question, though, is whether increased monitoring and surgical deliveries produced better perinatal outcomes. To that, the answer is “no.” Combined fetal and neonatal death rates in infants free of congenital anomalies were identical at 1 per 1000 in both groups (4 trials, 11,339 babies). The reviewers acknowledge that their meta-analysis of over 11,000 babies is still “underpowered,” i.e., too small to detect a difference in outcomes. However, they continue, the event is so rare in low-risk women that no trial or meta-analysis would likely be big enough to do so. Additionally, no differences were found for cases of hypoxic ischemic encephalopathy (1 trial, 2367 babies), admissions to neonatal intensive care (4 trials, 11,331 babies), neonatal seizure (1 trial, 8056 babies), evidence of multi-organ compromise within the first 24 hours (1 trial, 8056 babies), or even 5-minute Apgar scores less than 7 (4 trials, 11,324 babies).
The reviewers therefore conclude:
We found no evidence of benefit for the use of the admission CTG for low-risk women on admission in labour. Furthermore, the probability is that admission CTG increases the caesarean section rate by approximately 20%. . . . The findings of this review support recommendations that the admission CTG not be used for women who are low risk on admission in labour. Women should be informed that admission CTG is likely associated with an increase in the incidence of caesarean section without evidence of benefit (Devane 2012, p. 2). [Emphasis mine.]
According to the best evidence, the admission strip isn’t just ineffective, it’s harmful, and its use should be abandoned
Birthplace in England Collaborative Group. (2011). Perinatal and maternal outcomes by planned place of birth for healthy women with low risk pregnancies: the Birthplace in England national prospective cohort study. BMJ, 343, d7400. http://www.ncbi.nlm.nih.gov/pubmed/22117057?dopt=Citation
Devane, D., Lalor, J. G., Daly, S., McGuire, W., & Smith, V. (2012). Cardiotocography versus intermittent auscultation of fetal heart on admission to labour ward for assessment of fetal wellbeing. Cochrane Database Syst Rev, 2, CD005122. doi: 10.1002/14651858.CD005122.pub4 http://www.ncbi.nlm.nih.gov/pubmed/22336808