Continuous Electronic Fetal Monitoring (Cardiotocography) in Labor: Should It Be Routine?
Regular Science & Sensibility contributor and author Henci Goer takes a look at the recent Cochrane review “Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour” to determine if the researchers found any new information on the benefits or risks of CTG for normal, low risk labors. Read on to see if things might have changed and are the hospitals in your area conforming with recommendations of ACOG, SCOG and RCOG? Are these recommendations based on the evidence? - Sharon Muza, Community Manager, Science & Sensibility
Almost all women laboring in U.S. hospitals undergo continuous electronic fetal monitoring (EFM) (Declercq 2006), but should they? A new iteration of the Cochrane systematic review of randomized controlled trials of EFM versus intermittent auscultation (listening) can answer that question (Alfirevic 2013).
The rationale behind continuous EFM was that insufficient oxygen (hypoxia) in labor was a major cause of intrapartum fetal death and permanent brain injury. It was thought that enhanced ability to pick up changes in fetal heart rate (FHR) patterns signaling distress would enable doctors to rescue the fetus in time to prevent perinatal death and cerebral palsy. Does that theory hold up in practice?
According to the Cochrane review, not so much—nor, I might add, is this news since all prior versions have reported the same results. Continuous EFM fails to decrease perinatal mortality, whether in women overall (11 trials, 33,513 participants) or in the subgroups of high-risk women (5 trials, 1974 participants), mixed-risk/risk not specified populations (3 trials, 15,490 participants), or low-risk women (3 trials, 16,049 participants). Neither does it reduce incidence of cerebral palsy whether in women overall (2 trials, 13,252 women) or in high-risk women (1 trial, 173 participants) or in a mixed-risk/risk not specified population (1 trial, 13,079). (No trial reported comparative cerebral palsy rates in low-risk women.) In fact, cerebral palsy rates were increased more than two-fold (risk ratio: 2.54) in the EFM group in the sole high-risk trial reporting this outcome, although with only 173 women and one trial, it is unclear what, if anything, should be made of this. The authors, noting that the delay between diagnosis and taking action was longer in the EFM group, speculated that EFM may have been providing a false sense of feeling in control of the situation (Shy 1990). So it turns out more information isn’t necessarily better information.
Continuous EFM isn’t a total washout. It reduces the incidence of neonatal seizure, which is of some benefit since neonatal seizure can indicate permanent brain injury, the likelihood of which depends on the severity of seizure and whether it is accompanied by other symptoms. Among women overall (9 trials, 32,386 participants), it halved seizure rates (risk ratio: 0.50). In high-risk populations (5 trials, 4805 participants), it reduced seizure rates (risk ratio: 0.67), but the difference failed to achieve statistical significance while in low-risk populations (3 trials, 25,175 participants), the reduction was by nearly two-thirds (risk ratio: 0.36), and in mixed-risk/risk not specified populations (2 trials, 2406 participants), the reduction approached 80% (risk ratio: 0.18). The reviewers calculate that with a baseline seizure risk of 3.0 per 1000 labors among women overall in the intermittent auscultation group, 667 women would have to have continuous EFM in order to prevent 1 neonatal seizure. In low-risk women, in whom the baseline risk was 1.2 per 1000 labors with intermittent auscultation, my calculation raised that to 833 women.
Although continuous EFM fails in achieving its original goal of preventing perinatal death and cerebral palsy, the reduction in incidence of neonatal seizure would seem to argue for universal continuous EFM, were it not that this benefit comes at a price: continuous EFM increases the likelihood of cesarean surgery, and to a lesser degree, instrumental vaginal delivery, which increased among women overall by 15% (risk ratio: 1.15). Among women overall (11 trials, 18,861 participants), continuous EFM increased likelihood of cesarean by nearly two-thirds (risk ratio: 1.63); among high-risk women (6 trials, 2069 women), it doubled the risk (risk ratio: 1.91); it did the same (risk ratio: 2.06) among low-risk women (2 trials, 1431 participants) while among mixed-risk/risk not specified populations (3 trials, 15,361 participants), the rate was increased (risk ratio: 1.14), but the difference wasn’t statistically significant. The reviewers calculate that assuming a 15% cesarean rate with intermittent auscultation, one additional cesarean would be performed for every 11 women monitored, and 61 additional cesareans would be performed to prevent 1 seizure. In low-risk women, my calculation found that 1 additional cesarean would be performed for every 6 women monitored, and 76 additional cesareans would be performed to prevent 1 seizure.
The Cochrane reviewers conclude that women should be informed that EFM neither reduces perinatal mortality nor cerebral palsy and that while it reduces incidence of neonatal seizures, it does so at the cost of increased cesarean and instrumental vaginal deliveries. Cesarean and instrumental deliveries, I hardly need point out, have their own associated harms, some of them quite serious, and these must be set against the reduction in seizures (Childbirth Connection 2012; Goer 2012). The reviewers write:
Given the perceived conflict between the risk for the mother . . . and benefit for the baby . . . , it is difficult to make quality judgments as to which effect is more important. . . . The real challenge is how best to convey this uncertainty to women and help them to make an informed choice without compromising the normality of labour.
That gives us our marching orders, but how best might we carry them out? One reasonable course would be to see what obstetric guidelines advise.
The least decisive recommendation comes from the American Congress of Obstetricians and Gynecologists (2009), whose guidelines state: “Given that the available data do not show a clear benefit for the use of EFM over intermittent auscultation, either option is acceptable in a patient without complications” (p. 196). This suggests equivalency between the two, but, of course, they aren’t equivalent because continuous EFM increases likelihood of cesarean and instrumental vaginal delivery. ACOG further recommends that “the labor of women with high-risk conditions (eg, suspected fetal growth restriction, preeclampsia, and type 1 diabetes) should be monitored with continuous FHR monitoring” (p. 196), although they later acknowledge that this recommendation is based on “Level C” evidence, “expert opinion.”
The U.K. Royal College of Obstetricians and Gynaecologists takes a stronger stance: “Intermittent auscultation of the FHR is recommended for low-risk women in established labour in any birth setting” (p.155) (National Collaborating Center for Women’s and Children’s Health 2007). The Royal College advises switching to continuous EFM in low-risk women for these reasons:
- significant meconium, with consideration for making the switch with light meconium
- abnormal FHR is detected by intermittent auscultation
- maternal fever
- fresh bleeding developing in labor
- oxytocin use for augmentation [I would assume this would also cover oxytocin induction.]
- the woman’s request
The Canadian Society of Obstetricians and Gynaecologists provides the most detailed advice of all (Liston 2007). SOGC guidelines state: “Intermittent auscultation . . . is the recommended method of fetal surveillance [in healthy term women in spontaneous term labor who are free of risk factors for adverse perinatal outcome]” (p. S6). In women with risk factors for adverse perinatal outcome, the SOGC, like ACOG, recommends continuous EFM while acknowledging that “little scientific evidence” (p. S33) supports it. However, SOGC guidelines additionally state: “When a normal tracing is identified, it may be appropriate to interrupt the electronic fetal monitoring tracing for up to 30 minutes to facilitate periods of ambulation, bathing, or position change, providing that (1) the maternal-fetal condition is stable and (2) if oxytocin is being administered, the infusion rate is not increased” (p. S6).
The consistent recommendation that intermittent auscultation is preferable (in the case of RCOG and SOGC), or at least acceptable (in the case of ACOG), in low-risk women in spontaneous labor answers the question posed in the title. No, continuous EFM should not be routine, and we are on solid ground sharing this information and its sources with pregnant women.
Unfortunately, this doesn’t help most low-risk women laboring in U.S. hospitals because they will have either an epidural, be receiving oxytocin, or both. The SOGC guidelines can serve us here. With epidural analgesia, the guidelines state: “Intermittent auscultation may be used to monitor the fetus when epidural analgesia is used during labour, provided that a protocol is in place for frequent intermittent auscultation assessment (e.g., every 5 minutes for 30 minutes after epidural initiation and after bolus top-ups as long as maternal vital signs are normal)” (p. S6), and the SOGC guidelines treat induction and augmentation the same as women with risk factors, that is, with continuous EFM but permitting breaks if mother, baby, and oxytocin dose are stable. Suggesting that women in these categories request that their caregivers follow SOGC guidelines seems a pragmatic approach to achieving any benefits continuous EFM may provide while potentially reducing harms.
I could end here, but I can’t help asking: Why stop with search and rescue of hypoxic babies? Why not look at prevention? Among the 10,053 low-risk women at the Dublin Maternity Hospital, the neonatal seizure rates were 10 times (14 per 10,000 continuous EFM vs. 38 per 10,000 intermittent auscultation) those in the 14,618 women in the Dallas trial (1 per 10,000 continuous EFM vs. 4 per 10,000 intermittent auscultation) (Alfirevic 2013). I doubt that it’s coincidental that the Dublin Maternity Hospital is the home of Active Management of Labor, which prescribes routine early rupture of membranes and high doses of oxytocin with a short interval between dose increases for any woman not progressing at a minimum 1 cm dilation per hour. Early rupture of membranes, induction, and high-dose/short interval oxytocin regimens all increase stress on the fetus (Goer 2012). I think educators and doulas have a role to play here too. We can point women to Lamaze’s Healthy Birth Practices #1 and #4 to help them start a conversation with their care providers about labor induction and artificial rupture of membranes. And while women aren’t in a position to dictate oxytocin regimen, nurses and other hospital insiders can lobby for uniformly instituting the more physiologic oxytocin protocol found in Pitocin packaging if their hospital doesn’t mandate it already. An ounce of prevention is worth a pound of cure not the least because prevention has no adverse effects.
ACOG. (2009). Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles. ACOG Practice Bulletin No. 106. http://www.ncbi.nlm.nih.gov/pubmed/19546798
Alfirevic, Z., Devane, D., & Gyte, G. M. (2013). Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour. Cochrane Database Syst Rev, 5, CD006066. doi: 10.1002/14651858.CD006066.pub2 http://www.ncbi.nlm.nih.gov/pubmed/23728657
Childbirth Connection. (2012). Vaginal or Cesarean Birth: What Is at Stake for Women and Babies? New York. http://transform.childbirthconnection.org/reports/cesarean/
Declercq, E., Sakala, C., Corry, M. P., & Applebaum, S. (2006). Listening to Mothers II: Report of the Second National U.S. Survey of Women’s Childbearing Experiences. New York: Childbirth Connection. http://childbirthconnection.org/pdfs/LTMII_report.pdf
Goer, H., & Romano, Amy. (2012). Optimal Care in Childbirth: The Case for a Physiologic Approach. Seattle: Classic Day Publishing.
Liston, R., Sawchuck, D., & Young, D. (2007). Fetal health surveillance: antepartum and intrapartum consensus guideline. J Obstet Gynaecol Can, 29(9 Suppl 4), S3-56. http://www.sogc.org/guidelines/documents/gui197CPG0709r.pdf
National Collaborating Centre for Women’s and Children’s Health. (2007). Intrapartum care. Care of healthy women and their babies during childbirth. London: NICE. http://www.nice.org.uk/nicemedia/live/11837/36275/36275.pdf
Shy, K. K., Luthy, D. A., Bennett, F. C., Whitfield, M., Larson, E. B., van Belle, G., . . . Stenchever, M. A. (1990). Effects of electronic fetal-heart-rate monitoring, as compared with periodic auscultation, on the neurologic development of premature infants. N Engl J Med, 322(9), 588-593. http://www.ncbi.nlm.nih.gov/pubmed/2406602?dopt=Citation
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