ABSTRACT
Introduction It has long been known that labor is a risk factor for fetal mortality and for neonatal morbidity and mortality. Through research carried out in the 1950s, 1960s, and early 1970s, obstetricians obtained a better understanding of fetal respiratory physiology and human fetal physiology in response to the labor process. It provided a basis for diagnostic techniques to detect possible fetal well-being and compromise. It was appreciated that clinical management could change fetal conditions. In 1961 Saling introduced intermittent scalp pH measurement as the first technique for direct assessment of fetal well-being during labor.1 Fetal heart rate (FHR) monitoring technologies were developed in the 1950s and 1960s by Hammacher et al.,2 Hon and Quilligan,3 Caldeyro-Barcia,4 and others. By the late 1960s and early 1970s, equipment for intrapartum fetal evaluation was commercially available. In the 1970s, obstetricians had very optimistic expectations that with intrapartum surveillance (utilizing continuous FHR monitoring and intermittent fetal scalp pH determinations), intrapartum stillbirths and neonatal neurological injuries caused by intrapartum hypoxia could be significantly reduced or eliminated. The hope was that with continuous electronic FHR monitoring, “early asphyxia” will be recognized; through timely obstetrical intervention, asphyxiainduced brain damage, or neonatal death, will be avoided. Continuous electronic fetal monitoring (EFM) was introduced into widespread clinical practice before evidence from randomized clinical trials demonstrated either efficacy or safety. In the 1970s and 1980s, continuous electronic FHR monitoring became routine in most hospitals in the United States and the Western world. During the last 30 years, thousands of articles were written on this topic. Initial retrospective studies evaluated 135,000 patients and showed a more than threefold improvement in the intrapartum fetal death rate for the electronically monitored group versus the control group with intermittent auscultation (IA).5,6 Many randomized trials were performed comparing the efficacy and safety of routine continuous EFM with IA for intrapartum surveillance. Recently, there has been increasing utilization of central monitoring systems and computerized recognition and interpretation of fetal heart rate patterns.7-11
Despite the initial optimism, continuous fetal monitoring during labor has not resulted in reduced adverse neonatal
outcome, specifically cerebral palsy rate.12,13 Moreover, due to the high “false-positive” rate,14 cardiotocography (CTG) use resulted in an increased incidence of operative delivery for suspected “fetal distress.” It has been estimated that 11 cesarean deliveries are needed to prevent one case of hypoxic ischemic encephalopathy.12,13 During the past two decades, several techniques have been evaluated in an attempt to reduce the high false-positive rate of CTG and the resulting operative delivery rate. Fetal pulse oximetry was first described in 1989.15 Several randomized control trials (RCTs) were published in the ensuing decades that aimed to evaluate its value in reducing operative delivery rate without increasing fetal adverse outcome, but they showed equivocal results.
