Baseline rate is the approximate mean FHR rounded to increments of 5 bpm during a 10 min. segment, excluding: Periodic or episodic changes Periodic patterns are those associated with UC Episodic patterns are those not associated with UC Periods of marked FHR variability Segments of the baseline that differ by > 25 bpm o Baseline rate can be determined between UC Variability: Amplitude of FHR change Baseline Variability Description Undetectable from baseline Absent Visually detectable from baseline, ≤ 5 bpm Minimal (possible causes: fetal sleep, anomalies, hypoxia, meds) 5-25 bpm Moderate > 25 bpm Marked Non-Reassuring Fetal Status (definition and clinical therapy) Reassuring vs. non-reassuring FHR pattern : Reassuring characteristics include baseline rate of 110-160 bpm, present variability, and variability of at least 2 cycles per minute. Non-reassuring fetal status is indicated by persistent late decels, persistent severe variable decelerations, and prolonged decelerations. Fetal tachycardia : FHR baseline > 160 bpm for at least a 10-minute period Possible causes: o Maternal: fever, dehydration, anxiety, betasympathominmetic drugs (terbutaline, atropine), hyperthyroidism, supraventricular tachycardia
Catherine and Brooke’s awesome OB study guide 17 o Fetal: early fetal hypoxia, asphyxia, fetal anemia, infection, prematurity, prolonged fetal stimulation When fetal Tachycardia is assessed, assess for maternal fever, maternal dehydration, and maternal anxiety Fetal Bradycardia : FHR baseline < 110 bpm for at least a 10-minute period Possible causes: stimulation of vagus nerve (application of forceps or vacuum), drugs that stimulate the parasympathetic nervous system or block the sympathetic (anesthesia & regional analgesia), maternal hypotension, prolonged umbilical cord compression, fetal dysrhythmia, hypoxemia or late fetal asphyxia, accidental monitoring of maternal pulse When fetal bradycardia is assessed, assess for maternal hypotension, accidental maternal monitoring Sinusoidal pattern : Sinusoidal pattern is indicated by an undulating waveform evenly distributed between 120 and 130 bpm baseline. There is minimal variability. A FHR baseline pattern consisting of a series of cycles that are extremely smooth & regular in amplitude & duration Resembles a perfect letter “S” on its side May be benign Causes: o Fetal anemia o Chronic fetal bleeding o Fetal isoimmunization o Twin-to-twin transfusion o Umbilical cord occlusion o CNS malformations Accelerations: Visually apparent abrupt increase from FHR baseline Term infants: o Onset to peak < 30 seconds; acme ≥ 15 bpm o Duration ≥ 15 seconds < 2 minutes Preterm: o Onset to peak < 30 seconds; acme ≥ 10 bpm o Duration ≥ 10 seconds Prolonged acceleration duration ≥ 2 minutes < 10 minutes Decelerations: Abrupt: onset to nadir < 30 seconds Gradual: onset to nadir > 30 seconds Basic Tx: o Call for help!