Fetal Monitoring

Continuous electronic FHR monitoring is the most common obstetric procedure performed and used in 85% of laboring parturients in the United States. Early decelerations are identified by the symmetrical decrease in the FHR in relation to the uterine contraction. The onset of FHR deceleration to the nadir will occur in ≥30 s, with the onset occurring with uterine contraction and the nadir occurring at the peak of uterine contraction. The change in the FHR represents a nonhypoxic autonomic response caused by uterine compression onto the fetal head. Late decelerations can be identified by the delayed nature of the FHR in response to the onset of uterine contraction. FHR deceleration will occur after the start of a uterine contraction, and the FHR will reach a nadir of ≥30 s after the peak of uterine contraction. Late decelerations are a concerning finding that occurs when there is uteroplacental insufficiency. Variable decelerations are abrupt decreases in the FHR that are not associated with uterine contraction. The FHR should decrease by 15 bpm from baseline and last more than 15 s and less than 2 min. Variable decelerations can be caused by the transient compression of the umbilical cord from fetal movement or uterine contraction (Carter A, Nunes N. Evid Based Pract. 2019;22(12):11–2.).