It is a remarkable fact that, in the approximately 50 years of the clinical use of continuous electronic fetal heart rate (FHR) monitoring, we have still not yet reached consensus on interpretation and management recommendations for FHR patterns. I will examine the role of personalities, politics, and territoriality in explaining this difficulty in achieving such agreement.

The English language edition of Erich Saling’s book “Foetal and Neonatal Hypoxia in Relation to Clinical Obstetric Practice” was published in 1968. The translator, F. E. Loeffler, of St Mary’s Hospital, London, understatedly noted that “… some of the views expressed by Dr Saling … are rather unorthodox …”, but our interest is drawn to his couple of pages (of a total of 281 pages) that are devoted to continuous FHR pattern monitoring. Saling illustrated decelerations, which includes nomenclature espoused by both Hon and Quilligan and Roberto Caldeyro-Barcia et al, and commented that “… monitoring of the foetal heart will probably not prove sufficiently reliable for accurate assessment of the foetus”, because “… the factors influencing the foetal heart rate are too numerous to allow accurate conclusions …”. He briefly mentioned his fellow countryman, Hammacher, but omitted his recognition of the importance of FHR variability, which he called “oscillation.” Hammacher’s work is poorly known in the United States because he wrote only 1 English-language paper.

Meanwhile, Edward Hon was working away independently at Yale with his scalp electrodes (originally a metal Michel skin clip that was soldered to a connecting wire) and continuously depicting FHR patterns on a Gilson Recorder (Gilson Company, Inc, Lewis Center, OH), which was a huge vacuum-tube based device taller than he. The original recordings were on a logarithmic vertical scale, which was subsequently changed to an arithmetic scale. The paper speed that could be selected was 0.5 mm/sec, hence the origin of our conventional paper speed of 3 cm/min.

Roberto Caldeyro-Barcia, an articulate and urbane Uruguayan, was simultaneously making FHR observations, and, like Hon, recording FHR patterns, musing about their origins, and attempting to determine their cause. Caldeyro-Barcia spoke perfect English and was well-known in obstetrics circles in the United States and Europe.

An attempt was made to reconcile these independent observations in a meeting in Europe in the 1970s, which resulted in a degree of standardization. The major unreconciled difference was in paper speed; 3 cm/min became the standard in the United States, and 1 cm/min became the standard in Europe. The slower paper speed exaggerates the apparent FHR variability.

Hon published an excellent monograph entitled “An Atlas of Fetal Heart Rate Patterns” in 1968 that summarized his previous publications and contained theories on the mechanisms from the earliest days of FHR monitoring. It was published by Harty Press, in New Haven, CT; unfortunately, it is a poorly known work, possibly because it is plastic bound, quarto size, with pages duplicated rather than printed, and was prone to disintegration. Nevertheless, Hon was established as the major figure in FHR monitoring.

He began a remarkably fruitful collaboration with E. J. Quilligan, Chair of the Department of Obstetrics and Gynecology at Yale University. The 2 men moved to Los Angeles County/University of Southern California in the late 1960s to carry out intensive studies in FHR with the aid of a Research Delivery Room. The room was equipped fully for physiologic monitoring, processing blood gases, and archiving all of the data; the approximately 15,000 per annum deliveries allowed 1 labor and delivery to be studied intensively virtually each day. An army of fellows were introduced to research in this venue.

Despite all this productivity, there were some aspects of Hon’s work that were not universally accepted. His attractive triptych of early decelerations (head compression), late decelerations (uteroplacental insufficiency), and variable decelerations (umbilical cord compression) is a case in point. His earlier study that related early decelerations to head compression was performed by pressing a metal pessary against the presenting fetal head. The illustration in the resulting paper depicted what is clearly a variable deceleration, with an onset to nadir of the deceleration of <10 seconds, not the smooth rounded deceleration of later illustrations. The latter looked for all the world like late decelerations that had not yet become “late.” Incidentally, there had been much previous work, particularly from Germany, that showed that sufficient compression of the fetal head results in a variable deceleration.

The prevailing atmosphere in the United States also stressed the hazards of late decelerations without great emphasis on the fact that FHR variability was the trump card that modified the adverse significance of late decelerations. The use of ancillary tests was believed to be adequate to weed out the “abnormal” tracings that were falsely positive. The most popular technique was fetal blood sampling for pH and base excess measurement. This reliance on fetal blood sampling, which in fact never achieved popularity in community hospitals in the United States, lasted until 1985, when Clark and Paul from Los Angeles County/University of Southern California showed that a huge reduction in the use of fetal blood sampling did not result in an increase in newborn infant morbidity. As these authors stated, an obstetrician’s need for fetal blood sampling is in inverse proportion to his understanding of FHR pattern interpretation; focusing on FHR variability and accelerations would be more appropriate.

A most important paper resulted from a reanalysis of many of the earlier FHR recordings from Yale. In this publication Paul et al classified 3 gradations of late decelerations based on their depth and dichotomized them based on whether they had “average” or “reduced” FHR variability. They showed convincingly that fetal scalp pH decreased with the depth of the decelerations and that this was even more striking with reduced variability. The mean pH was 7.09 ± 0.05 SD in the presence of severe late decelerations with reduced variability, where the FHR nadir was ≥45 beats/min below baseline. The uniqueness of these data are all the more so because they had 28 fetuses in that group. Those studies will never be repeated because it would now be unethical not to intervene with this FHR pattern.

Despite all this activity and dissections of FHR patterns, consensus on interpretation of the FHR record (ie, its significance for fetal acidemia), and management recommendations (ie, how to use the emerging FHR pattern to avoid acidemia) were slow in coming. International efforts were made by the International Federation of Gynecology and Obstetrics, the Royal College of Obstetricians and Gynecologists, the Society of Obstetricians and Gynaecologists of Canada, the Royal Australian and New Zealand College of Obstetricians and Gynaecologists and others, but none achieved widespread international consensus.

It is little appreciated today that one of the aims of the first National Institute of Child Health and Human Development Research Planning Workshop was to develop a consensus for FHR pattern management; however, the efforts failed because of an inability of the 18 participants to reach agreement. The final document ended with a “Clinical Statement,” which defined the normal trace and concluded that fetuses with this pattern were at no risk for damaging acidemia. They also defined a pattern in which the fetus is at high risk of potentially damaging acidemia, that is, absent variability in the presence of decelerations or a bradycardia. All other patterns between these were relegated to a zone of “no consensus.”

These 3 subsequently became the 3 categories that were defined by the 2008 National Institute of Child Health and Human Development (NICHD) Conference ; the implication was that no progress had been made in subcategorizing most FHR patterns, those in category II, in the previous 11 years!

The American College of Obstetricians and Gynecologists accepted the FHR nomenclature of the 1997 NICHD workshop in 2005 in a Practice Bulletin and the nomenclature of the 2008 NICHD meeting in a Practice Bulletin of 2009. The reaction of perinatologists to the 3 categories of the 2008 NICHD publication was substantial. At least 1 dozen abstracts appeared at the Society of Maternal-Fetal Medicine and Society of Gynecologic Investigation in 2010 (the first opportunity for presentation since the 2008 publication of the second NICHD conference), and more were presented at these conferences in 2011.

The excessive heterogeneity of category II was noted by many authors, and the impossibility of using this category for management recommendations was emphasized. A number of authors compared outcomes with the 3-category system vs a 5-tier system that was based on risk of acidemia. The 5-tier system also included the risk that a pattern would evolve to one with a higher risk of acidemia as labor progressed. This is a well-recognized happening, but also to one with little objective data to allow prediction.

Meanwhile, in the midst of the reaction, the American College of Obstetricians and Gynecologists put out a further Practice Bulletin in 2010 that presented what could be considered as 8 categories that were based on different decelerations or other features of the FHR pattern. This clearly had the makings of recommendations for management, and each of the categories noted that FHR variability modified one’s reaction to management of the pattern. However, it did not appear to be a major step in simplification of management for the clinicians (ie, the physician, midwife, or nurse on the front line).

Meanwhile, the 5-tier color-coded FHR interpretation and management system was enthusiastically accepted in Japan, under the encouragement of the Japan Society of Obstetrics and Gynecology. It has penetrated widely to 70% of birth units, and data on effectiveness are being established. One small study showed a 7-fold reduction in the incidence of metabolic acidemia (base excess of umbilical arterial blood at birth ≤12 mEq/L) with no significant change in cesarean or vacuum extractor delivery rates. Subsequent analysis showed that this reduced metabolic acidemia was due to a reduction of fetuses who had variable, prolonged, and late decelerations and bradycardias. This implies that the 5-tier system with its rigid emphasis on standardized nomenclature and classification allowed better selection of those patients who had intervention for fetal indications.

Further support for the effectiveness of this 5-tier system of interpretation and possibly treatment is seen in an analysis of almost 2500 newborn infants with variable outcome. The incidence of metabolic acidemia and encephalopathy at birth were related to both the degree and duration of FHR-tracing abnormality. Another study compared 5 FHR experts who used strict rules for the interpretation of the 5-tier color-coded system and showed remarkable agreement in examination of the last 3 hours before birth of 30 fetuses. Again, further support is evident in the abstracts at the recent meetings of the Society for Maternal-Fetal Medicine and Society for Gynecologic Investigation, although the works are not yet presented in detail.

The current remarkable activity on the part of many organizations and individuals in the field of FHR monitoring, interpretation, and management suggests that we are within reach of achieving consensus on management algorithms ion the coming years. This will be a highly desirable first step towards testing these approaches for effectiveness.