Technical Update No. 429: Maternal Heart Rate Artefact During Intrapartum Fetal Health Surveillance

Abstract

ObjectiveTo improve perinatal outcomes and minimize provider error by increasing awareness of strategies to detect intrapartum maternal heart rate artefact and to respond when such artefact is suspected. Target PopulationAll pregnant patients during labour. OptionsMaternal heart rate artefact may be detected based on clinical features or through technology. Suspected maternal heart rate artefact may be assessed by applying a fetal scalp electrode (preferred) or through external fetal monitoring, augmented by point-of-care sonography (alternative). OutcomesUnrecognized intrapartum maternal heart rate artefact increases the risk that abnormal/atypical fetal heart rate patterns will go undetected and, hence, the risk of adverse perinatal outcomes. Benefits, Harms, and CostsUnrecognized maternal heart rate artefact can lead to adverse perinatal outcomes (hypoxic-ischemic encephalopathy, fetal death, and neonatal death) and adverse maternal outcomes (unnecessary cesarean delivery or operative vaginal delivery). Timely recognition of such artefact may avoid these adverse outcomes. The costs of early recognition of maternal heart rate artefact are relatively small: increased use of fetal scalp electrodes and point-of-care sonography, as well as additional assessments by the health care provider. The cost savings are significant, as a result of lower risk of adverse perinatal outcomes. Potential harms are false-positive diagnoses of maternal heart rate artefact, expediting delivery unnecessarily when the fetal status cannot be reliably determined but is normal, and the rare complications associated with increased use of fetal scalp electrodes. EvidenceTwo PubMed searches were completed. The first was for articles published between January 1, 1970, and November 25, 2021, using the medical subject headings (MeSH) “fetal monitoring” and “artifacts” (38 articles). The second was for articles published during the same period using the MeSH “fetal monitoring” and “maternal heart rate” (841 articles). Validation MethodsThe authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional [weak] recommendations). Intended AudienceAll health care providers involved in obstetrical care. SUMMARY STATEMENTS1.If maternal heart rate artefact is unrecognized and a concerning fetal heart rate is masked by a maternal heart rate tracing that mimics a normal/atypical fetal heart rate tracing, there is an increased risk of intrapartum fetal death, neonatal death, neonatal acidemia at birth, and hypoxic-ischemic encephalopathy (low).2.If maternal heart rate artefact is unrecognized and a normal fetal heart rate is masked by a maternal heart rate tracing that mimics an atypical/abnormal fetal heart rate tracing, there is an increased risk of unnecessary intervention, including cesarean delivery or operative vaginal delivery (low).3.In late-first and second stage of labour, fetal and maternal heart rates are frequently within the same range. As a result, the risk of maternal heart rate artefact is greatest and the artefact is most difficult to detect, often involving a subtle switch between the 2 signals, with no discernable change in baseline rate (moderate).4.Maternal heart rate artefact is common during external fetal heart rate monitoring (moderate) and intermittent auscultation (low). It also occurs, but less frequently, with internal fetal monitoring (low). RECOMMENDATIONS1.Clinicians should be aware that modern fetal monitors may seamlessly transition from capturing the fetal heart rate to capturing the maternal heart rate with no apparent break in the tracing (strong, low).2.Clinicians should consider the possibility of maternal heart rate artefact when monitoring the fetal heart rate. A high index of suspicion is indicated when the presumed fetal heart rate is similar to the maternal heart rate; abruptly improves from a previously atypical/abnormal pattern without an explanation; shows accelerations during contractions and/or maternal pushing; demonstrates wide variations, changes in baseline heart rate, or an abrupt change in variability; demonstrates halving or doubling in the baseline heart rate; and/or is difficult to interpret (strong, low).3.We recommend that the obstetrical care team be aware of technology to detect maternal heart rate and understand how to use it (strong, low). When maternal heart rate detection technology is available, we suggest using it whenever performing fetal heart rate monitoring (conditional, low) and we recommend using it in the following circumstances: when the maternal heart rate is elevated to within the fetal range, when artefact is suspected on the basis of clinical features (see Recommendation 2), and during the active second stage of labour (strong, low).4.Health care providers performing intermittent auscultation should assess the maternal pulse and initiate continuous electronic fetal monitoring if the maternal heart rate is similar to the fetal heart rate (strong, low).5.When maternal heart rate artefact is suspected on the basis of clinical features during electronic fetal monitoring and/or on the basis of coincidence alarms, we recommend taking the following steps in an escalating fashion until artefact is ruled out: (1) optimize position of the fetal heart rate transducer and initiate continuous monitoring of the maternal heart rate with a pulse oximeter if not already started; (2) perform point-of-care sonography, if available, to confirm the fetal heart rate, and position the external fetal heart rate transducer under direct vision; and (3) apply a fetal scalp electrode if there are no contraindications (preferred) and/or augment continuous external fetal monitoring with continuous or repeated point-of-care sonographic assessments (if available) of the fetal heart rate (alternative, less preferred because of its limitations) (strong, low).6.If there is ongoing suspicion of maternal heart rate artefact and uncertainty about whether the fetal heart rate tracing is accurate despite attempts at optimization, we recommend expediting delivery, depending on the overall clinical context (strong, low).7.We advise vigilance concerning intrapartum maternal heart rate artefact at the initiation of fetal heart rate monitoring (conditional, low). Health care providers should be aware of reported cases of undiagnosed intrauterine fetal death, in which the maternal heart rate was interpreted as the fetal heart rate and an emergency cesarean delivery was performed. If this clinical scenario is suspected, we suggest point-of-care sonography to directly visualize the fetal heart rate before cesarean delivery, provided this technology is available and visualization can be performed within an acceptable timeframe, given the overall clinical context (conditional, low).8.When maternal heart rate detection technologies are unavailable, we suggest that the maternal heart rate be continuously monitored with a pulse oximeter during intrapartum fetal heart rate monitoring (conditional, low) and recommend vigilance concerning the clinical features of maternal heart rate artefact (strong, low).9.We recommend following the same principles in the previous recommendations during delivery for multiple gestation. However, these deliveries are more complex and require additional vigilance because maternal heart rate artefact may occur with one or more of the fetuses. As well, health care providers should be vigilant concerning the possibility of multiple gestation heart rate artefact, which occurs when 2 or more fetal heart rate signals are confused and/or 2 fetal heart rate transducers are inadvertently monitoring the same fetus (strong, low).