What is Non-Reassuring Cardiotocography (CTG)?
Non-reassuring CTG refers to fetal heart rate patterns that indicate potential fetal compromise, including fetal tachycardia, bradycardia, loss of heart rate variability, and variable or late decelerations. 1
Specific CTG Patterns Defining Non-Reassuring Status
Non-reassuring fetal status on CTG is characterized by the following abnormal patterns:
- Fetal tachycardia: Baseline fetal heart rate persistently above 160 beats per minute 1
- Fetal bradycardia: Baseline fetal heart rate persistently below 110 beats per minute 1
- Loss of heart rate variability: Absence of normal beat-to-beat fluctuations in the fetal heart rate 1
- Variable decelerations: Abrupt decreases in fetal heart rate that vary in timing, depth, and duration 1
- Late decelerations: Gradual decreases in fetal heart rate with delayed onset after contraction begins, with the nadir occurring after the peak of contraction, indicating uteroplacental insufficiency and fetal hypoxemia 2
Clinical Significance and Urgency
The presence of non-reassuring fetal status should prompt urgent obstetric and medical review because emergency cesarean delivery may be necessary. 1
- Non-reassuring CTG patterns can indicate fetal hypoxia and distress, though CTG has a high false positive rate 3
- Late decelerations specifically indicate uteroplacental insufficiency and require immediate intervention, not continued observation 2
- When accompanied by loss of variability, late decelerations are associated with fetal acidosis and increased risk of adverse neonatal outcomes 2
Context-Specific Interpretation
In Maternal Critical Illness (e.g., Sepsis, Cardiac Arrest)
- Fetal surveillance provides a real-time measure of maternal end-organ perfusion and can help optimize maternal positioning, oxygenation, and mean arterial pressure 1
- Non-reassuring fetal well-being could be the first sign of deterioration of maternal clinical condition and may signify impending maternal decompensation 1
- Most non-reassuring tracings will improve with maternal hemodynamic optimization during initial stabilization 1
In Fetal Growth Restriction (FGR)
- CTG monitoring frequency should be increased when FGR is complicated by absent or reversed end-diastolic velocity in umbilical artery Doppler 1, 4
- In the setting of reversed end-diastolic velocity, heightened surveillance with CTG at least 1-2 times per day is recommended 1
Important Clinical Pitfalls
Many factors other than hypoxia can cause non-reassuring CTG traces, leading to high false positive rates and unnecessary interventions. 3
- Non-reassuring CTG is the second leading cause of primary cesarean delivery in the United States 5
- Prolonged fetal heart rate decelerations do not uniformly predict poor fetal outcome but can prompt unnecessary cesarean delivery 5
- Significant inter- and intra-observer variability exists in CTG interpretation, which can lead to both under-treatment and over-treatment 6
- When prolonged decelerations occur, rechecking fetal heart tones in the operating room may reveal return to baseline, potentially avoiding unnecessary cesarean delivery 5
Management Approach
When non-reassuring CTG patterns are identified:
- Immediate interventions: Administer oxygen to the mother, position on left side, and discontinue oxytocin if being administered 2
- Multidisciplinary team approach: Interpretation and management should involve obstetrics, maternal-fetal medicine, and anesthesia when appropriate 1
- Consider multiple factors: Source of any maternal infection, gestational age, maternal and fetal health status, and patient preferences 1
- Delivery indications: Non-reassuring cardiotocograph is an indication for delivery in preeclampsia and an indication for cesarean section in FGR with absent or reversed end-diastolic velocity 1