Solving the Obstetrical Paradox: The FETAL Technique—A Step toward Noninvasive Evaluation of Fetal pH

Abstract

Every year, about 85 percent of the approximately 5 million births in North America are evaluated with the electronic fetal monitoring (EFM). Clinicians use the EFM as a proxy to assess fetal oxygenation status, fetal well-being, and potential compromise. Despite the widespread use of this technology, neonatal hypoxia and acidosis continue to make up a high proportion of neonatal morbidity at term. Indeed, though the fetal heart rhythm is inextricably linked to fetal acid-base status, EFM has not been shown to reliably predict neonatal pH status nor has it reduced adverse maternal or neonatal outcomes. As a consequence, the high false-positive rate of EFM for predicting adverse neonatal outcomes has led to an increase in the rate of operative vaginal and cesarean delivery, with elevated rates of associated maternal and neonatal morbidity. This fact invariably leads to a paradox we have henceforth defined as the “obstetrical paradox.” Herein, we explore the potential solutions to this paradox and introduce a novel noninvasive technique to assess fetal acid-base status in utero known as the “FETAL technique” (Fourier Evaluation of Tracings and Acidosis in Labour). The FETAL technique, currently under investigation, applies the discrete Fourier transformation to EFM tracings to determine the spectral frequency distribution of the fetal heart rate. These specific frequency distributions correlate with specific umbilical pH values and may provide the missing link between fetal heat rate patterns and acid-base status at birth. As we work toward realizing the full potential benefits of EFM, finding the best assessment strategies to evaluate fetal pH in real time remains a key goal in obstetrics.