Misidentification of Maternal Heart Rate as Fetal on Cardiotocography During the Second Stage of Labor: The Role of the Fetal Electrocardiograph

摘要

Cardiotocography (CTG), a screening test for fetal hypoxia during labor, is a continuous graphic record of fetal heart rate (FHR) and uterine contractions. During the second stage of labor, if the abdominal transducer is moved downward to improve the signal quality of the CTG trace, the transducer can pick up sound waves reflected by movements of maternal vessels. This results in recording of maternal heart rate (MHR), which may mimic the FHR and lead to an adverse outcome because the fetus is not monitored during the time of hypoxic stress. Cardiotocography relies on pattern recognition; therefore, clinicians must have a thorough understanding of the features of MHR that differentiate it from FHR during labor.