Am Fam Physician. 1999 May 1;59(9):2416-2422.
In the 1960s and 1970s, continuous electronic fetal monitoring (EFM) was introduced with the idea that it would help clinicians diagnose fetal hypoxia in time to prevent perinatal neurologic damage. By the early 1990s, more than 75 percent of the nation's birth attendants had switched from intermittent auscultation to EFM.1
However, more recently, a number of systematic reviews of randomized controlled trials have been published that do not support the routine use of EFM, especially in low-risk women.2–5 The data show that neurologic abnormalities are not caused by intermittent episodes of asphyxia that commonly occur during labor and delivery. The Cochrane Collaboration2 concluded that, compared with intermittent auscultation, EFM does not reduce the rate of perinatal deaths, the rate of APGAR scores below 7 or the number of infants admitted to neonatal intensive care. Moreover, EFM was found to result in higher rates of cesarean section (relative risk: 1.33, confidence interval: 1.08 to 1.59) and total operative deliveries (relative risk: 1.23, confidence interval: 1.15 to 1.31).
The U.S. Preventive Services Task Force states that there is “fair” evidence that “routine EFM for low-risk women in labor is not recommended.”3 For high-risk women, the task force states, “There is insufficient evidence to recommend for or against EFM . . .” The Canadian Task Force on the Periodic Health Examination made a similar recommendation.4 A technical bulletin from the American College of Obstetricians and Gynecologists states that either EFM or intermittent auscultation is acceptable and acknowledges the risk of increased intervention with continuous monitoring.5
Furthermore, outcomes are the same regardless of whether fetal distress is managed operatively or conservatively.6,7 Because intervention that is chosen on the basis of the fetal heart rate does not seem to improve outcomes, it is possible that we should not be monitoring by any method. Unfortunately, all of the randomized, controlled trials of EFM have compared continuous with frequent intermittent monitoring. Until we have a controlled study comparing monitored women with unmonitored women, we will continue to spend considerable health care resources without knowing whether monitoring fetal heart tones is even necessary. However, it is unlikely that this type of study will be done.
If our best evidence-based guidelines no longer recommend EFM, why are so many clinicians still using it? It seems simple to abandon a technology that has failed to live up to its promise. Nevertheless, there are educational, legal, technical and financial barriers to changing clinical practice.
First, since the advent of EFM, many nurses and physicians have not been trained in intermittent auscultation. For clinicians to feel comfortable using auscultation, more training opportunities will have to be developed.
Second, some physicians believe that EFM might still be a valuable assessment tool with better guidelines for interpreting tracings and making management decisions.8 In this issue of American Family Physician, Sweha and colleagues9 review the current literature on the interpretation of fetal heart rate monitoring. However, many studies comparing the ability of experts to agree on the interpretation of an EFM tracing have shown poor inter-rater reliability, even in controlled research settings with expert clinicians.10,11
To address this problem, the National Institutes of Health and the International Federation of Gynecology and Obstetrics have established criteria for interpreting EFM strips.12 Also, the possibility of using computer-generated interpretations to make more objective assessments is being studied.13,14 These efforts may someday produce effective methods for interpretation and clinical decision-making. Currently, no such method exists.
Third, physicians may fear that they will be vulnerable to malpractice lawsuits if they do not use EFM. The impact of changing to intermittent monitoring on malpractice claims is unknown. However, as long as patients are counseled and intermittent auscultation is performed diligently, physicians can be confident that they are following current recommendations. Furthermore, tracings are frequently used to justify claims that action should have been more aggressive or timely despite the fact that EFM has a low positive predictive value for fetal compromise.15–18
In one study,19 reviewers were given two identical tracings and antenatal histories but were told that the outcome was good in one case and poor in the other. When the outcome was poor, the reviewers were more likely to disagree with the obstetrician's interpretation and management. This study demonstrates the danger of retrospective reviews of fetal heart tracings by expert witnesses.19,20 If hospital clinical policies support intermittent auscultation, it might prove easier to defend a management decision based on a carefully documented clinical assessment rather than on an EFM tracing.
A fourth reason that physicians may favor EFM is that many hospitals are not adequately staffed to do intermittent auscultation. Studies that show intermittent auscultation to be equivalent or better than EFM had 1:1 ratios of nurses to patients and fetal heart tones were assessed every 15 to 30 minutes during the first stage of labor and every five minutes in the second stage. In one study,21 a university hospital center attempted to use intermittent auscultation as the primary method of monitoring without increasing the number of staff. Auscultation was only successfully completed in 31 of 862 patients in labor with viable fetuses. Intermittent auscultation was abandoned for most patients because the staff was not able to maintain the required 1:1 nurse-patient ratio.
Reducing cesarean section rates and equipment needs might partially offset the costs of hiring additional staff to perform intermittent auscultation. Nevertheless, routine use of intermittent auscultation is likely to be more expensive than EFM. Although no data are available to indicate whether adopting intermittent auscultation reduces costly malpractice claims, it is possible that if EFM tracings were not used retroactively to question physician judgment, reducing legal costs could make intermittent auscultation financially viable. Other solutions to the staffing problems might include hiring trained birth attendants instead of registered nurses to do the monitoring. Continuous labor support has also been shown to decrease intervention and increase patient satisfaction.22,23
Intermittent auscultation is a “high-touch, low-tech” method that lowers the number of cesarean sections performed because of fetal distress. This is safer for mothers and reduces the need for consultatation, which can disrupt the doctor-patient relationship. Family physicians are at the forefront of overcoming the challenges of implementing evidence-based guidelines. They are in an ideal position to introduce intermittent monitoring to their hospitals because they often spend a significant amount of time at their patients' bedside and usually only have one patient laboring at a time.
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