Electronic Fetal Monitoring

Electronic fetal monitoring (EFM) records the fetal heart rate (FHR) and uterine activity. It does not measure fetal oxygen tension or pH directly. The tracing is an indirect signal of how the fetus is responding to interruptions in oxygen transfer along the maternal–placental–fetal pathway. That distinction prevents a common error: treating one abnormal feature as proof of fetal acidemia. A tracing becomes more concerning when several findings fit the same physiological story, such as recurrent late decelerations with reduced variability, or a prolonged deceleration that does not recover. Moderate variability is reassuring because it reflects ongoing autonomic nervous system activity; it is the single most reliable indicator that the fetus is not currently acidemic, although it does not guarantee future well-being. EFM must therefore be interpreted with the mother and the uterus in view. Maternal hypotension after neuraxial analgesia, fever, hypoxaemia, bleeding, placental dysfunction, cord compression, excessive uterine activity, and oxytocin exposure can all alter the tracing. The experienced nurse first asks, “What changed in the maternal or uterine environment?” rather than simply naming the pattern. Continuous EFM also has...