Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Intermittent auscultation and cardiotocography principles
Obstetrics and gynaecology · UK scope · Sources checked 7 Sept 2026 · Clinical review pending
!
Prolonged deceleration or acute bradycardia
An acute bradycardia or a single deceleration lasting three minutes or more requires urgent obstetric review and preparations for urgent birth. The response must address possible cord prolapse, placental abruption, rupture or reversible maternal causes.
Action: Call for obstetric help, confirm that the recorded rate is fetal, assess the clinical situation and stop oxytocin if running. Reposition away from supine, correct identified hypotension and consider tocolysis for excessive contractions. Prepare for urgent birth and neonatal support; expedite if bradycardia persists for nine minutes, or earlier when risk factors or an acute event justify it.
Purpose and principles
Choose appropriate fetal monitoring, interpret heart-rate patterns alongside the clinical situation, and respond promptly when changes suggest evolving compromise.
Fetal heart monitoring seeks evidence that the baby is tolerating the physiological stress of labour. Intermittent auscultation provides regular samples of the heart rate while preserving mobility and avoiding a continuous trace in low-risk labour. CTG records the fetal heart pattern and uterine activity over time and becomes appropriate when risk or findings justify closer surveillance. The choice should be explained and reviewed, because a pregnancy initially considered low risk may develop intrapartum complications.
A CTG is an indirect physiological signal. A reassuring trace reduces concern at that moment but does not guarantee the rest of labour will remain uncomplicated. An abnormal trace can have reversible causes, including excessive contractions or maternal hypotension, and does not automatically mean established fetal injury. Good interpretation combines the trace with gestation, medication, progress, maternal observations and events such as membrane rupture. Record a clinical assessment and action plan rather than a classification alone.
Key points
Practice
Two practice questions
Your practice draft is saved in this browser.
Question 1 of 2
0 correct
Obstetrics and gynaecologyOriginal SBA
A newly observed late deceleration
During oxytocin augmentation, a CTG shows a baseline of 145/minute and normal variability, but clearly identified late decelerations have appeared over the last several contractions. Under current NICE classification, how should the deceleration feature be categorised?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 7 Sept 2026; clinical approval remains outstanding.
Monitoring assesses fetal response to labour; it does not diagnose hypoxia from one isolated number.
Offer intermittent auscultation during established labour when maternal and fetal risk remains low.
Listen for at least one minute immediately after a palpated contraction, at least every fifteen minutes in first stage and every five minutes in second stage.
Assess the four CTG features: contractions, baseline, variability and decelerations, then combine them with risk factors and change over time.
A normal CTG has four white features; one amber feature is suspicious; any red feature or two or more amber features is pathological.
Absence of accelerations on an otherwise normal intrapartum CTG does not by itself indicate fetal acidosis.
Do not give maternal oxygen solely to treat an abnormal CTG when maternal oxygenation is normal.
Indications, selection and cautions
Selecting intermittent auscultation
Low-risk women in established labour should be offered intermittent assessment with a Pinard stethoscope or Doppler. Review fetal growth, gestation, maternal conditions and new symptoms. Explain the method and the circumstances that would prompt a recommendation for CTG.
Reasons to consider continuous monitoring
Antenatal or intrapartum concerns such as a uterine scar, fetal growth problems, significant hypertension, suspected infection, abnormal auscultation or oxytocin use can indicate CTG. Meconium should trigger discussion and a full risk assessment rather than being interpreted without its character and associated findings.
Maternal and fetal signal confusion
Maternal pulse can be mistaken for the fetal rate, particularly during pushing when maternal tachycardia is common. Compare the signals and seek help if uncertainty persists. Sudden apparent accelerations in the second stage should prompt consideration that the monitor has switched to the maternal pulse.
Reading the trend
A baseline within the usual range can still be concerning if it has risen substantially from earlier in labour. Similarly, worsening deceleration recovery or altered variability may matter before a prolonged threshold is reached. Review previous recordings during the systematic hourly assessment.
Red flags requiring action
Acute fetal bradycardia or a deceleration lasting at least three minutes requires urgent review and preparations for birth.
Late decelerations are a red CTG feature regardless of whether they are repetitive or how long they have been present.
Method and interpretation
01Intermittent auscultationFirst step
Why
Sample fetal heart rate in labour without identified complications.
Interpretation and limitations
Listen after a palpated contraction for at least one minute, at least every fifteen minutes in first stage and every five minutes in second stage. Record a single rate and any heard accelerations or decelerations. Check maternal pulse hourly in first stage and simultaneously during second-stage auscultation.
02CTG contractions and baseline
Why
Assess uterine workload and the underlying fetal heart rate.
Interpretation and limitations
Count contractions and their duration; five or more in ten minutes or hypertonus is amber and requires measures to reduce frequency. Establish the mean baseline over a stable ten-minute period. A stable 110–160/minute is white; below 100 or above 160 is red. A rise of at least 20/minute, 100–109 or an indeterminate baseline is amber.
03CTG variability
Why
Assess oscillation around the baseline between accelerations and decelerations.
Interpretation and limitations
Variability of 5–25/minute is white. Below 5 for 30–50 minutes is amber and beyond 50 minutes is red; above 25 for up to ten minutes is amber and beyond ten minutes is red. A sinusoidal pattern is red. Opioids or fetal sleep may reduce variability, but accompanying risk factors must still be assessed.
04CTG deceleration assessment
Why
Assess the timing, recovery and evolution of heart-rate reductions.
Clinical next steps
01Low-risk monitoringAuscultate and reassess the whole situationFirst stepEstablished labour continues without an indication for continuous cardiotocography.+
1Explain the monitoring plan, obtain agreement and complete the stage-appropriate auscultation with maternal pulse checks.
2Review maternal observations, contractions, progress and any new risk factors at least hourly, documenting the findings.
3If the rate rises by at least 20/minute from the start of labour or a deceleration is heard, listen more frequently, for example after three consecutive contractions, and perform a full review.
4If concern is confirmed, summon help and recommend CTG; reassess the monitoring method again if a temporary concern resolves and no continuing indication remains.
02CTG interpretationClassify features and choose a responseContinuous monitoring is underway and a systematic trace assessment is due or a change occurs.+
Procedure and medicine safety
Reduces uterine activity when excessive contractions contribute to fetal concern.
Terbutaline for excessive contraction frequency
A suggested NICE acute regimen is terbutaline 250 micrograms, equivalent to 0.25 mg, by subcutaneous injection. Give after assessment and while stopping or reducing an oxytocin infusion where relevant.
Review maternal cardiovascular status and potential tachycardia or metabolic effects. Confirm the injection concentration, monitor the response and do not let tocolysis delay indicated urgent birth.
Risks, monitoring and follow-up
Perform and document a systematic maternal and fetal assessment hourly or more often when concern exists, reviewing earlier traces and changes over time.
Check signal quality throughout labour, particularly after movement, procedures and the onset of active pushing; unresolved signal loss requires action.
After any corrective measure, reassess whether the trace and the underlying clinical problem have improved, and retain a clear escalation threshold.
Record the time urgent review was requested, the response, decisions about birth and any subsequent recovery of the fetal heart rate.
After birth, retain the trace and ensure neonatal colleagues know about significant intrapartum abnormalities and the reason for expedited delivery.
Special situations
A stable borderline baseline needs context
A baseline of 100–109/minute is amber, but NICE allows usual care if it has remained stable throughout labour with normal variability and no variable or late decelerations. This exception does not apply to a new falling rate.
Late means recovery after the contraction
Assess the relationship to the contraction rather than assigning a label from shape alone. The current NICE classification places late decelerations in the red category without requiring repetition or a thirty-minute observation period.
Classification is not a countdown
A red feature communicates the need for urgent assessment but does not mean every abnormality has the same cause or urgency. Conversely, important clinical deterioration may demand action before a numerical duration threshold is reached.
The contraction trace has limitations
An external tocodynamometer helps record timing and frequency but does not reliably quantify the absolute strength of contractions. Palpation and clinical assessment remain relevant when judging uterine activity or possible obstruction.
Common pitfalls
01
Counting an absent acceleration as proof of fetal acidosis on an otherwise normal intrapartum trace.
02
Waiting thirty minutes before treating late decelerations as a red feature.
03
Calling a trace reassuring without confirming that it is recording the fetal heart.
04
Giving oxygen or large fluid boluses routinely for fetal changes when there is no maternal indication.
05
Treating the nine-minute bradycardia point as permission to postpone review or preparation for birth.
06
Documenting suspicious or pathological without describing the clinical context and management response.
Absent variability, a sinusoidal pattern or prolonged abnormal variability requires assessment of the whole clinical picture with a low threshold for escalation.
New decelerations with a rising baseline, maternal fever, bleeding or slow progress increase concern for compromise.
An apparently reassuring trace that may be recording the maternal pulse needs immediate signal verification.
Interpretation and limitations
Early decelerations and non-evolving uncomplicated variable decelerations are white. Concerning variable features include duration over sixty seconds, reduced variability within the dip, poor return to baseline or lost shouldering. Repetitive concerning variables for under thirty minutes, or non-repetitive concerning variables continuing over thirty minutes, are amber. Repetitive concerning variables lasting over thirty minutes are red. Late decelerations are red regardless of duration or repetition; an acute bradycardia or single prolonged deceleration lasting at least three minutes is also red.
05Digital fetal scalp stimulation
Why
Seek an additional physiological response when the clinical situation warrants it.
Interpretation and limitations
For a suspicious CTG with other risk factors, an acceleration followed by sustained trace improvement can support continued monitoring. Absence of an acceleration is concerning and may prompt expedited birth. NICE cannot recommend fetal blood sampling because evidence is limited; it should not be presented as an obligatory next step.
1Confirm patient identity, recording time, signal quality and that the fetal rather than maternal rate is being recorded.
2Describe contractions, baseline, variability and decelerations, assign feature colours and combine them into normal, suspicious or pathological classification.
3For a suspicious trace, assess the cause and implement appropriate conservative measures; additional maternal or fetal risks lower the threshold for urgent review.
4For a pathological trace, obtain urgent obstetric and senior midwifery review, assess reversible causes and agree whether birth needs to be expedited.
5Document the assessment, actions, communication and reassessment interval so that another clinician can understand both the classification and its consequences.
03Acute or persistent abnormalityTreat reversible causes while preparing escalationEscalationThere is a prolonged deceleration, pathological trace or worsening fetal concern.+
1Assess for an acute event including cord prolapse, abruption or uterine rupture and expedite birth when that diagnosis warrants it.
2Encourage a different maternal position and avoid supine positioning; check blood pressure and treat identified hypotension, including anaesthetic review after an epidural-related fall.
3Reduce or stop oxytocin and consider a tocolytic when contraction frequency is excessive; do not give routine intravenous fluid solely for a fetal heart abnormality without hypotension or sepsis.
4For a deceleration reaching three minutes, obtain urgent review and prepare birth; persistent bradycardia at nine minutes requires expedited birth, with earlier action for significant additional risks.
5If the heart rate recovers before that point, reassess the birth decision using the complete clinical picture and discuss the updated plan with the patient.