Table 4

Overview of parameters associated with fetal ANS

MethodsParametersDescriptionAssociated autonomic functionOver the course of pregnancyInterpretation
Doppler ultrasound, CTG, dMMG (marker), fMCG, BPPfHRFetal heart rateSympathetic and parasympathetic activityDecreases slightly over GA115 116
(normal range: 110–150 beats/min)117
Pathological fHR:<100 beats/min or >170 beats/min with a bandwidth of <5 and ≥90 min → indicates an insufficient fetal oxygen supply
fHRVFetal heart rate variabilitySympathetic and parasympathetic activity (sympatho-vagal balance)Increases with GA42 118An increase is associated with vagal and sympathetic activity which may be associated with the ability to respond to regulatory mechanisms48 119 120
Fetal bradycardia and tachycardiaFetal bradycardia: fHR <110 beats/min121
Fetal tachycardia: fHR >180 beats/min, present for more than at least 50% of the examination time122
Irregularities in fHR rhythmFetal arrhythmias are detected in at least 2% of unselected pregnancies during the routine obstetrical ultrasound122Occurrence >10 min increases the risk of preterm delivery and higher perinatal morbidity and mortality.122 Transient sinus bradycardia:<2 min have no clinical implication123
Doppler ultrasound, CTG, dMMG (marker), fMCG, BPPFetal body movementsCan be indirectly detected through fMCG beginning at 18 GA41fHRIncreases over the course of pregnancy
A reduction in fetal movements is associated with adverse pregnancy outcomes in pregnancy124
  • ANS, autonomic nervous system; BPP, biophysical profile; CTG, cardiotocography; dMMG, diaphragmatic magnetomyogram ; fHR, fetal heart rate; fHRV, fetal heart rate variability; fMCG, fetal magnetocardiography; GA, gestational age; HRV, heart rate variability.