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    Opinion: New FHR monitoring standards: Something old and something new

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    Obstetricians have been trying to link the fetal heart rate (FHR) with fetal health since the invention of the modified stethoscope by Pinard in the 1870s. Practical application of intrapartum FHR assessment, however, required the development of an electronic fetal monitoring (EFM) system based on the fetal ECG by Drs. Edward Hon and Orvan Hess at Yale in the late 1950s. Their discovery allowed for precise estimations of FHR baselines and periodic changes in a continuous fashion. Within a decade, clinicians throughout the United States had adopted EFM.



    Unfortunately, the inconvenient truth about EFM is that it was introduced before its efficacy could be confirmed by hard-core research. Developed primarily to reduce the occurrence of cerebral palsy (CP) and intrapartum stillbirth, its value in preventing these outcomes has never been proven. In fact, it's the secondary benefit of fetal monitoring—providing a convenient way to supervise several patients at one time—and our fear of litigation that are the primary reasons it survives. So EFM remains perhaps the most prominent example of universal adoption of a medical technology before its verification.

    The shortcomings of electronic FHR monitoring

    The available data suggest that continuous intrapartum EFM does not perform much better than the intermittent auscultation of Pinard. A Cochrane meta-analysis that included over 37,000 patients, for instance, concluded that while its application cut neonatal seizures in half (RR 0.50; 95% CI, 0.31–0.80), it failed to affect perinatal mortality or CP rates.1 The same meta-analysis also revealed that continuous EFM increased cesarean (RR 1.16; 95% CI, 1.01–1.32) and operative vaginal (RR 1.16; 95% CI, 1.01–1.32) deliveries. In fact, as ACOG reports, the false-positive rate of EFM for CP exceeds 99%, with as few as 1 to 2/1,000 fetuses with nonreassuring patterns developing CP.2

    The specificity of EFM may be improved with fetal scalp stimulation and scalp pH. A heart rate acceleration stimulated by digital pressure on the fetal scalp is highly correlated with a normal fetal pH (negative likelihood ratio 0.08; 95% CI, 0.02–0.41), although its absence is not always associated with acidosis in the setting of a worrisome tracing.3 Scalp pH testing can be employed at this point with a value of <7.20 (mixed venous) typically used as an indication for delivery, although its use appears to be rapidly decreasing across the country.

    Because of the false-positive rates of these approaches, additional methods of assessing fetal status in labor have been introduced under more rigorous testing, with mixed results. Fetal pulse oximetry has been compared to EFM in several clinical trials but the research to date shows no difference in overall cesarean delivery rates, although fewer of them were performed for nonreassuring fetal status (RR 0.68; 95% CI, 0.68–0.99).4 These studies also didn't show differences in any maternal or neonatal outcomes. More promising is the STAN fetal heart monitor, an FDA-approved device that takes Dr. Hon's original technology of monitoring the fetal ECG and uses specialized software to examine specific changes in the ECG related to fetal hypoxemia. Its use is suggested only in higher-risk patients who are likely to develop metabolic acidosis, rather than as a substitute for standard EFM. The most recent Cochrane review of STAN, which incorporated nearly 10,000 patients, showed reduced rates of metabolic acidosis and neonatal encephalopathy as well as operative vaginal deliveries without influencing cesarean rates.5

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    Christian M. Pettker, MD
    DR. PETTKER is Assistant Professor, Department of Obstetrics, Gynecology and Reproductive Sciences, Yale-New Haven Hospital, New Haven, ...
    Charles J Lockwood, MD, MHCM
    Dr. Lockwood, Editor-in-Chief, is Dean of the Morsani College of Medicine and Senior Vice President of USF Health, University of South ...

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