Key takeaways

  • A cardiotocograph (CTG) records two things at once: the fetal heart rate (top line) and your contractions (bottom line).
  • Clinicians read every trace using four features in order — baseline rate, variability, accelerations, and decelerations.
  • FIGO 2015 (adopted by FOGSI) sorts tracings into normal, suspicious, and pathological, each with a defined response.
  • Most abnormal traces have a healthy baby at birth — CTG has a high false-positive rate, so it must be read with the full clinical picture.
  • For low-risk labour, intermittent listening is as safe as continuous CTG and avoids unnecessary caesareans; continuous CTG is for higher-risk pregnancies.
  • A normal trace is strongly reassuring in the moment but does not guarantee a complication-free birth — other things, like cervical progress, also matter.

What a Fetal Heart Tracing Actually Measures

A fetal heart tracing is a continuous graphical record of your baby's heart rate over time, displayed alongside a recording of your uterine contractions. Together this is called cardiotocography (CTG): cardio for the heart, toco for contractions (Greek for childbirth), and graphy for the recording.

The top line is the fetal heart rate in beats per minute (bpm), usually on a scale running from 60 to 200. The bottom line is uterine activity — it rises with each contraction and falls between them. The trace moves at a standard speed (commonly 1 cm or 3 cm per minute) so the shape of any pattern can be assessed over time.

There are two ways to pick up the heartbeat:

  • External monitoring uses an ultrasound transducer strapped to your abdomen over the baby's heart. It is non-invasive, can be used before your waters break, and is suitable for most labour-room use.
  • Internal monitoring uses a small electrode clipped to the baby's scalp through the cervix, after the membranes have ruptured. It gives a cleaner, more accurate trace and is reserved for when external monitoring is unreliable or very precise interpretation is needed.

Not every labour needs continuous CTG. WHO, NICE, FIGO, and FOGSI all support intermittent auscultation — listening with a Pinard stethoscope or hand-held Doppler at set intervals — as the standard for low-risk labour. Continuous CTG is recommended when there is a recognised risk factor, which we cover below.

The Four Features Every CTG Is Assessed On

Clinicians do not read a trace by gut feel. They use a structured assessment — recommended by FIGO and used in FOGSI practice — based on four features, looked at in this order over at least ten minutes of tracing (ideally with the last 20–30 minutes available for context). A trace read for less than ten minutes can mislead.

1. Baseline heart rate — the average fetal heart rate over a ten-minute window, ignoring accelerations and decelerations. The normal range is 110–160 bpm. Below 110 is bradycardia; above 160 is tachycardia. Mild tachycardia (160–180 bpm) is most often caused by maternal fever, infection, dehydration, or certain medications. Marked tachycardia or persistent bradycardia needs urgent assessment.

2. Baseline variability — the small beat-to-beat fluctuation, measured as the bandwidth between the highest and lowest points each minute. Normal is 5–25 bpm. Reduced variability (under 5 bpm for more than 50 minutes) can mean the baby is asleep, a medication effect, or genuine compromise. Increased variability above 25 bpm (saltatory pattern) may suggest acute oxygen stress.

3. Accelerations — transient rises of 15 bpm or more lasting 15 seconds or more. Their presence is reassuring and is one of the strongest single signs of a well-oxygenated baby. Their absence is not alarming on its own, especially in active labour when accelerations naturally reduce.

4. Decelerations — transient dips of 15 bpm or more lasting 15 seconds or more. The shape, depth, duration, and timing relative to contractions are the most important diagnostic clues. Because they matter so much, decelerations get their own section below — including the difference between Early Decelerations in Labour: Why They Happen and When to Worry and Late Decelerations on the CTG: What They Mean in Labour patterns.

FIGO 2015 Three Categories: Normal, Suspicious, Pathological

The FIGO 2015 intrapartum guidance — adopted by FOGSI for Indian labour rooms — sorts every trace into three categories that drive what happens next. The simplicity is the point: each category has a clear action threshold.

Normal. All four features in range: baseline 110–160 bpm, variability 5–25 bpm, no repetitive decelerations (accelerations may be present or absent). Management is to continue routine care and reassess each hour or with any change. A normal trace is the strongest moment-to-moment evidence that your baby is not short of oxygen.

Suspicious. One feature abnormal but the others normal — for example a baseline of 100–110 or 160–180 bpm, reduced variability beyond 50 minutes, or repetitive variable decelerations without other concerning features. Management is conservative corrective action:

  • reposition to the left side (improves blood flow to the placenta)
  • give IV fluids if dehydrated
  • stop or reduce oxytocin if contractions are too frequent
  • check blood pressure and treat low pressure after an epidural
  • give oxygen if maternal oxygen levels are low
  • a vaginal examination to exclude bleeding or cord prolapse

Reassess after 30 minutes. If it returns to normal, labour continues; if it persists or worsens, the consultant is involved and delivery may be brought forward.

Pathological. Two or more abnormal features, or any single severe feature — such as repetitive late decelerations for 30 minutes or more, a single prolonged deceleration over 5 minutes, a sinusoidal pattern, or persistent bradycardia under 100 bpm. Management is urgent consultant escalation, immediate conservative measures, and active steps to expedite birth — either operative vaginal delivery (if you are fully dilated and the head is low enough) or an emergency caesarean.

Decelerations: Why Early, Variable, and Late Are Not the Same

Decelerations are the most clinically important — and most often misread — feature on a CTG. Not all dips mean trouble. FOGSI practice groups them into ones that are physiological (no urgent action) and ones that need active assessment, layered on top of the classic early/variable/late naming.

Early decelerations begin and end with the contraction, mirror its shape, are shallow, and are caused by harmless compression of the baby's head as it descends. They are common in late first stage and second stage and need no intervention. We cover them in depth in our guide to early decelerations in labour.

Simple (uncomplicated) variable decelerations are abrupt V-shaped drops from transient cord compression. When they are shallow, brief, recover quickly, and the rest of the trace is normal, they are reassuring and need no urgent action.

Atypical variable decelerations add concerning features — slow return to baseline, persistence beyond the contraction, loss of the small rises on either side ('loss of shoulders'), reduced variability within the dip, duration over 60 seconds, or repeated drops below 70 bpm. These need escalation.

Late decelerations start after the peak of the contraction and return to baseline after the contraction ends. That lag is the diagnostic clue. They suggest uteroplacental insufficiency — the placenta isn't delivering enough oxygen to buffer the brief squeeze of a contraction. Repetitive late decelerations are among the strongest CTG predictors of fetal oxygen stress, which is why our late decelerations guide treats them as a warning sign. The same placental problem underlies conditions like intrauterine growth restriction, where umbilical artery Doppler monitoring is used antenatally.

For concerning decelerations, the response is: conservative measures at once, involve the consultant, consider fetal scalp lactate or pH testing if available, and prepare to expedite delivery if the pattern persists.

Continuous CTG vs Intermittent Listening: What the Evidence Says

This has been one of the most debated questions in modern obstetrics. Continuous CTG was introduced in the 1970s in the hope it would dramatically cut cerebral palsy and stillbirth in labour. Decades of large randomised trials showed something more nuanced: continuous CTG roughly halves the rate of newborn seizures compared with intermittent listening, but it does not reduce cerebral palsy or perinatal death — and it substantially increases caesarean and instrumental deliveries because of its high false-positive rate.

The evidence-based conclusion, supported by Cochrane reviews and endorsed by WHO, NICE, FIGO, and FOGSI, is that continuous CTG should be reserved for pregnancies with identifiable risk factors, while low-risk labour can be safely monitored by intermittent listening.

FOGSI indications for continuous CTG include any of:


Most women who arrive in labour at an Indian tertiary or corporate hospital have at least one of these, which is why continuous CTG has become the default there.

Intermittent auscultation is the standard for low-risk labour. The technique is to listen for one minute immediately after a contraction — every 15 minutes in the first stage and every 5 minutes in the second stage. Any abnormal finding triggers a switch to continuous CTG. Its advantages are real: it keeps you mobile, supports upright positions, encourages a more physiological labour, and avoids the cascade of intervention that can follow an over-read trace. Its main requirement is one-to-one midwifery care, which is not feasible in every Indian unit.

Common CTG Patterns and What They Usually Mean

  • Normal reactive trace — baseline 120–160 bpm, variability 10–15 bpm, accelerations present, no decelerations. The gold standard, reliably indicating a healthy, non-stressed baby.
  • Variable decelerations in early second stage — baseline and variability preserved, occasional shallow variable dips with quick recovery. Usually intermittent cord compression as the baby descends; well tolerated. Left lateral position and IV fluids help.
  • Atypical variable decelerations — variable dips with concerning features (slow return, loss of shoulders, prolonged duration). Needs escalation and consideration of expediting delivery if birth is not close.
  • Late decelerations — repetitive dips that start after the contraction peak and return after it ends. Even when shallow, the most concerning routine pattern, suggesting uteroplacental insufficiency. Management is urgent.
  • Prolonged deceleration — a single drop lasting over three minutes; over five minutes is pathological. Causes include placental abruption, cord prolapse, uterine over-stimulation from oxytocin, low blood pressure after epidural, or a maternal seizure. Recovery after conservative measures is reassuring; failure to recover means urgent delivery.
  • Loss of variability — normal baseline but variability under 5 bpm for over 50 minutes. May be a sleeping baby (variability returns within ~40 minutes), a medication effect (opioids, magnesium sulphate), or genuine compromise. Persistent loss with no recovery is concerning.
  • Sinusoidal pattern — a smooth, wave-like baseline lasting over 30 minutes. Pathological; indicates severe fetal anaemia (for example from feto-maternal haemorrhage or severe Rh disease) and requires emergency delivery.

The Limitations of CTG — Why Context Always Matters

CTG is a useful tool, but it has well-known limitations that every clinician and informed parent should understand.

High false-positive rate. Most babies with an abnormal trace are perfectly healthy at birth with no evidence of injury. An abnormal CTG raises suspicion that must be acted on — but it is not proof of compromise.

It must be read in context. A trace interpreted in isolation — without your vital signs, labour progress, recent medication, position, gestation, and risk factors — can mislead in both directions, falsely alarming or falsely reassuring. A normal trace tells you about the heart, not about cervical progress, descent, or other parts of labour.

Inter-observer variability. Experienced obstetricians often disagree on the same trace, especially in the suspicious middle ground. This is why structured four-feature review, team discussion, and consultant second opinion are built into modern protocols. FOGSI training uses standardised CTG cases, and most Indian tertiary centres run regular CTG audit meetings.

Impact on labour itself. Continuous CTG can restrict mobility (wireless monitoring is improving this), encourage the supine position which is suboptimal for fetal oxygenation, and increase intervention.

FOGSI guidance is explicit: CTG is one tool among many, must be interpreted in clinical context, conservative measures should come before escalation, consultant review is mandatory for any suspicious or pathological trace, and the reasoning behind every step should be documented. Adjuncts such as fetal scalp blood sampling (pH or lactate) and scalp stimulation are available in well-equipped Indian centres and can clarify an ambiguous trace — but they support, rather than replace, the structured four-feature interpretation. The same logic applies before labour, where antenatal fetal monitoring such as NST and BPP is used to decide timing of birth.

Reading the CTG in Your Own Labour: What Parents Should Know

Many partners and family members try to read the machine. A little orientation helps, but the goal is to understand — not to self-diagnose.

  • The top line is the baby's heart rate; with all well it moves roughly between 110 and 160.
  • The bottom line is your contractions; it rises during each one and falls between them.
  • The display numbers show the current heart rate and how many contractions occur per ten minutes (typically three to five in active labour).

What parents should not do is make clinical decisions from the trace. The patterns are complex and self-reading tends to produce false alarm or false reassurance. What you can do is notice whether staff are reviewing the trace regularly, ask about any change that worries you, and request a consultant review if you feel the trace looks different from before. In a well-run labour room following FOGSI and LaQshya protocols, the trace is formally reviewed about every 30 minutes in active labour, with the review documented.

The single most useful question you or your partner can ask is: "How does the CTG look right now?" This invites the team to explain the current status in plain words. A more specific version is: "What is the FIGO category at the moment?" Most modern Indian obstetricians welcome this engagement — it makes the conversation clearer and decisions more transparent. Including monitoring preferences in your birth plan, and reviewing a list of questions to ask before labour, helps you have these conversations calmly rather than in a crisis. In short: the CTG is not the labour — it is one important input. The decisions are made by the team based on the full picture.

Myths vs Facts

When to Speak Up During CTG Monitoring

  • you notice the machine alarming repeatedly and no one has come to look at the trace
  • you feel a sudden, sharp, or constant pain that is different from your contractions
  • you have fresh vaginal bleeding, or you feel something in the vagina after your waters break (possible cord prolapse — a true emergency)
  • your baby's movements feel very different from usual
  • you develop a severe headache, visual disturbance, or upper-abdominal pain (possible signs of pre-eclampsia)
  • the trace clearly looks different from before and no one has explained why

Frequently asked questions

Does an abnormal CTG mean I will need a caesarean?

Not necessarily. Most suspicious traces settle with simple measures such as changing position to your left side, IV fluids, or reducing oxytocin. A caesarean is considered only when a trace is genuinely pathological and persists despite these measures, or when there is a single severe feature. The decision is made on the whole picture, not on the trace alone.

Why does the machine keep alarming if my baby is fine?

CTG machines alarm on any reading outside preset limits, and the external transducer can also lose contact when you move or the baby shifts, producing artefact. Frequent alarms are common and usually harmless. What matters is that a trained clinician reviews the actual trace, not the alarm. It is fine to ask, "How does the CTG look?"

Will continuous CTG stop me from moving around in labour?

Traditional wired CTG does restrict movement, which is one reason it is reserved for higher-risk labour. Many well-equipped Indian centres now offer wireless or waterproof telemetry monitoring that lets you stay mobile and upright. If mobility matters to you, ask in advance whether wireless monitoring is available and note your preference in your birth plan.

Can I refuse continuous CTG?

If your pregnancy is genuinely low-risk, intermittent listening is an evidence-based, equally safe alternative, and you can discuss it with your team. If you have a recognised risk factor, continuous monitoring is recommended for your baby's safety. The right approach is a shared conversation — ask why it is being advised in your specific case.

What is the difference between a CTG and an NST?

They use the same kind of monitor. A CTG in labour records the fetal heart rate against contractions to guide intrapartum decisions. A non-stress test (NST) is the same technology used before labour, usually in the third trimester, to check fetal wellbeing in higher-risk pregnancies. Our guide to antenatal fetal monitoring explains the NST and biophysical profile in detail.

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