Abstract
Since the 1970s, electronic fetal monitoring (EFM) also known as cardiotocography (CTG) has been used extensively in labor around the world, despite its known failure to help prevent many babies from developing neonatal encephalopathy and cerebral palsy. Part of EFM's poor performance with respect to these outcomes arises from a fundamental misunderstanding of the differences between screening and diagnostic tests, subjective classifications of fetal heart rate (FHR) patterns that lead to large inter-observer variability in its interpretation, failure to appreciate early stages of fetal compromise, and poor statistical modeling for its use as a screening test. We have developed a new approach to the practice and interpretation of EFM called the fetal reserve index (FRI) which does the following: (1) breaking FHR components down into 4 components, (heart rate, variability, accelerations, and decelerations); (2) contextualizing the metrics by adding increased uterine activity; (3) adding specific maternal, fetal, and obstetric risk factors. The result is an eight-point scoring metric that, when directly compared with current American College of Obstetricians and Gynecologists EFM categories, even in version 1.0 with equal weighting of variables, shows that the FRI has performed much better for identifying cases at risk before damage had occurred, reducing the need for emergency deliveries, and lowering overall Cesarean delivery rates. With increased data, we expect further refinements in the specifics of scoring that will allow even earlier detection of compromise in labor.