Baseline fetal HR: Normal HR is 110–160 bpm
Fetal tachycardia: HR > 160 bpm. Causes: Maternal or fetal fever/infxn, fetal hypoxia, thyrotoxicosis, maternal meds (β-agonists and parasympathetic blockers)
Fetal bradycardia: HR < 110 bpm, w/ severe bradycardia <90 bpm. Causes: Hypoxia, complete heart block, maternal meds (β-blockers)
Variability: Absence of beat-to-beat variability may indicate: Severe hypoxia, anencephaly, complete heart block, maternal med effect (narcotics, MgSO4)
Accelerations: Are associated with fetal movement and indicate fetal well-being
Decelerations
Early: Assoc w/ uterine compression of fetal head. Benign; not assoc w/ compromise
Variable: Assoc w/ umbilical cord compression. Can cause perinatal depression, but if beat-to beat variability is maintained, then fetus is not compromised
Late: Assoc w/ uteroplacental insuff. If beat-to-beat variability maintained, fetus usually well compensated. If not, then may represent significant fetal hypoxia
Fetal heart rate interpretation
Category I: Normal (ALL of: HR 110–160, moderate variability, +/− accels, no late or variable decels, may have early decels → routine care)
Category II: Indeterminate (any abnormality, requires surveillance and re-eval)
Category III: Abn (sinusoidal pattern OR absent variability w/ recurrent late decels, recurrent variable decels, or brady. Resolve cause expeditiously)