Latest Update on Cardiotocography (CTG)
The most significant recent development in CTG interpretation is the recognition that current classification systems remain inadequate, with 2024 evidence showing that among five major international templates (FIGO 2015, NICE 2017/2022, Swedish 2009/2017), NICE 2022 demonstrates the highest sensitivity (92%) for detecting fetal acidemia and is considered the safest current classification system, though all templates still suffer from either low sensitivity or low specificity. 1
Core CTG Interpretation Framework
The established DR C BRAVADO mnemonic remains the systematic approach for CTG interpretation 2:
- DR (Determine Risk): Assess clinical risk status (low/medium/high)
- C (Contractions): Rate, rhythm, frequency, duration, intensity, resting tone
- BRA (Baseline Rate): Normal 110-160 bpm; bradycardia <110 bpm; tachycardia >160 bpm
- V (Variability): Absent, minimal, moderate (normal), or marked
- A (Accelerations): ≥15 bpm rise lasting ≥15 seconds (≥10 bpm for ≥10 seconds if preterm)
- D (Decelerations): Absent, early, variable, late, or prolonged
- O (Overall Assessment): Three-category NICHD classification system
Three-Category Classification System
The NICHD categorization divides tracings into 2:
Category I (Normal):
- Moderate baseline variability
- Normal baseline FHR (110-160 bpm)
- No late or variable decelerations
- Management: Continue current monitoring
Category II (Indeterminate):
- All tracings not Category I or III
- Includes: bradycardia without absent variability, tachycardia, minimal/absent/marked variability, absent accelerations after stimulation, recurrent variable or late decelerations without absent variability
- Management: General measures (position change, check vitals, oxygen, IV fluids, discontinue oxytocin); consider expedited delivery if abnormalities persist
Category III (Abnormal):
- Absent baseline variability WITH recurrent late/variable decelerations, bradycardia, OR sinusoidal pattern
- Management: Discontinue oxytocin; expedite delivery (operative vaginal or cesarean)
Critical 2026 Updates
Physiological Integration Approach
A major conceptual shift emphasizes interpreting CTG as a maternal-fetal physiologic system rather than isolated pattern recognition 3. Global guidelines now define uterine activity across multiple physiologic parameters and integrate these with fetal heart rate, while US guidelines focus primarily on tachysystole (>5 contractions per 10 minutes) without explicit definitions of other uterine physiologic parameters 3.
The physiological interpretation approach focuses on distinguishing fetal compensation from decompensation, recognizing that gradually evolving hypoxic stress during labor is expected, and most fetuses mount adequate compensatory responses 4. This individualized approach has shown emerging evidence for reducing both hypoxic-ischemic encephalopathy (HIE) rates AND emergency cesarean sections 4.
Monitoring Strategy for Low-Risk Pregnancies
For low-risk pregnancies, structured intermittent auscultation (IA) is recommended over continuous CTG 2:
Structured IA Protocol:
- Frequency: Every 15-30 minutes in active first stage; every 5 minutes in second stage with pushing
- Procedure: Count FHR for ≥60 seconds between contractions for baseline; count for 60 seconds after contraction to assess fetal response
- Indications for assessment: Before labor-enhancing procedures, medications, analgesia; after admission, membrane rupture, vaginal exam
Admission CTG in low-risk pregnancies shows no improvement in maternal or neonatal outcomes and is NOT recommended 5. A 2026 meta-analysis of 16,341 women found admission CTG only increased continuous monitoring use (RR 1.23) without reducing cesarean sections, NICU admissions, or low Apgar scores 5.
Key Performance Limitations
Common pitfall: All current CTG classification systems have significant limitations 1:
- High sensitivity systems (NICE 2022, Swedish 2009: 92%) have low specificity (62-63%)
- High specificity systems (Swedish 2017, FIGO 2015: 90-91%) have very low sensitivity (39-42%)
- Positive predictive values remain poor across all systems (15-24%)
- Negative predictive values are excellent (95-99%)
This means CTG is better at ruling out acidemia than ruling it in, and pathological tracings frequently occur without actual fetal compromise.
Intrauterine Resuscitation Interventions
When Category II or III tracings occur 2:
- Change maternal position (left lateral preferred)
- Assess maternal vital signs (temperature, BP, pulse)
- Discontinue oxytocin
- Administer maternal oxygen (recent evidence shows significant effect on fetal oxygenation in abnormal patterns)
- IV fluid bolus
- Vaginal examination (check for cord prolapse, assess progress)
- Consider amnioinfusion for recurrent deep variable decelerations (reduces cesarean delivery, low Apgar scores, and low cord pH)
- Fetal scalp stimulation (if acceleration occurs, pH likely ≥7.20)
- Consider tocolytics (terbutaline) to transiently stop contractions
Critical caveat: Tocolytics improve FHR tracings but have NOT shown improvements in neonatal outcomes 2.
Emerging Technologies
Fetal electrocardiography (FECG) with ST-segment analysis (STAN) reduces operative vaginal deliveries (NNT=50) and fetal scalp sampling (NNT=33), plus decreases neonatal encephalopathy and acidosis 2. However, it requires ruptured membranes and internal scalp monitoring.
Fetal pulse oximetry has NOT demonstrated reduction in cesarean delivery rates and is not recommended 2.
Central digital fetal monitoring (vs. paper CTG) shows no difference in neonatal metabolic acidosis or other outcomes, though it may reduce instrumental vaginal deliveries for suspected hypoxia 6.
Predictive Value by Labor Stage
Second-stage CTG parameters are most predictive of acidemia 7:
- Beat-to-beat variability in second stage: AUC 0.992
- Baseline FHR in second stage: AUC 0.914
- Progressive reduction in variability across labor stages strongly predicts acidemia
- Late decelerations during second stage are particularly concerning
Documentation Requirements
Adequate documentation is essential for medicolegal protection 2:
- Regular review by physicians and nurses throughout labor
- Flow sheets/partograms recommended
- Electronic archival processes
- Written information on tracings must coincide with automated processes
- Cord arterial pH <7.00 or base deficit >12 mmol/L is one of four essential criteria for determining acute intrapartum hypoxic event sufficient to cause cerebral palsy
Bottom Line
Despite decades of use, continuous EFM has only demonstrated benefit in reducing neonatal seizures, with no reduction in cerebral palsy or neonatal mortality 2. The technology's primary value lies in its high negative predictive value—normal tracings reliably indicate fetal well-being. However, abnormal tracings have poor positive predictive value, leading to increased cesarean and operative vaginal deliveries without proportionate improvements in outcomes. The future lies in physiological interpretation that integrates uterine and fetal parameters as a unified system, combined with judicious use of intermittent auscultation in low-risk patients.