Intrapartum CTG interpretation — structured oral station (12 minutes)

Opening prompt — "Describe this trace for me."

Model response — never lead with an opinion: ^[1][2]

• "I would describe it systematically: contractions first, then baseline rate, baseline variability, accelerations, decelerations — and then I would put it back into the clinical picture."
• "Before anything else I want to know this is the fetal heart rate, so I would palpate the maternal pulse while I look at the trace, or have maternal pulse oximetry displayed on the same recording."
• "I also want the clinical picture: gestation, how long she has been on oxytocin and at what rate, when the epidural went in, her blood pressure and temperature, liquor colour, station and progress, and what the trace looked like an hour ago."^[2][1]

Examiner is listening for: a fixed order, the maternal pulse check unprompted, and the clinical picture requested before a verdict. ^[2]

Probe 1 — "The midwife is right to be unsure. How do you settle whether it is the mother or the baby?"

• "Maternal heart rate confusion is the most dangerous artefact in intrapartum monitoring, and the trace can look entirely reassuring while it happens."^[2][1]
• "I palpate her radial pulse against the trace. I look for a rate that has jumped by exactly half or double. In the second stage I treat accelerations that coincide precisely with every push as maternal until proven otherwise."
• "If I cannot resolve it, I use bedside ultrasound. If I still cannot separate the two rates, I expedite birth — an uninterpretable trace in an at-risk labour is an abnormal finding, not a technical nuisance."^[2][1]

Probe 2 — "Confirmed fetal. Baseline has risen from 130 to 165, variability is 4 bpm, no accelerations, and there are late decelerations. Classify it."

• "Using the RANZCOG feature framework: a normal intrapartum CTG is baseline 110 to 160, variability 6 to 25, accelerations present and no decelerations. This trace has four abnormal features."^[2]
• "Baseline above 160 and rising, and late decelerations, are both features that require action. Late decelerations occurring with reduced variability place this in the highest grade — likely fetal compromise, requiring immediate action. Two action-level features together, or one that persists, also escalate to that grade."^[2][1]
• "In FIGO 2015 terms this is a pathological trace. In NICHD terms it is Category II heading towards Category III, which needs absent variability with recurrent late decelerations."^[1]

Probe 3 — "Why do late decelerations mean what they mean?"

• "Intervillous perfusion falls during each contraction and recovers between them, so the interval is the fetal oxygen window. When placental reserve is inadequate, the fall in oxygen during the contraction is sensed by the peripheral chemoreflex, and the resulting deceleration lags the contraction — hence the late timing."^[4][1]
• "Variability tells me about central integration. Reduced variability means the brainstem is no longer having its usual conversation with the heart, so late decelerations with reduced variability tell me compensation is failing, not just being tested."^[4][2]
• "Contrast that with variable decelerations, which are cord compression and a chemoreflex the healthy fetus can sustain for hours, and early decelerations, which are head compression and a vagal reflex."^[4][1]

Probe 4 — "Manage her. Be specific."

• "Stop the oxytocin" — first, before anything else, in an augmented labour with an abnormal trace.^[2]
• "Full lateral position; intravenous fluid bolus; check and correct her blood pressure, with a vasopressor and urgent anaesthetic review if the epidural has dropped it."^[2]
• "Vaginal examination to exclude cord prolapse and assess station and progress."
• "If uterine activity remains excessive after stopping the oxytocin, terbutaline 250 micrograms subcutaneously; sublingual glyceryl trinitrate 400 micrograms or intravenous salbutamol 100 micrograms are alternatives depending on the local formulary."^[6][2]
• "I would not give her facial oxygen for the trace. Her saturations are normal, and maternal oxygen supplementation in a normoxaemic woman does not improve umbilical artery pH or neonatal outcomes."^[5]
• "I would call my consultant to the bedside, alert theatre, anaesthetics and the neonatal team, and document the time of each call."^[2]

Probe 5 — "The rate falls to 60 bpm and stays there. Talk me through it with times."

• "Emergency call. Full lateral, fluids, blood pressure corrected, oxytocin already stopped. Vaginal examination now to exclude cord prolapse, and I am thinking about abruption and, in a scarred uterus, rupture. I confirm the signal is fetal."^[2][1]
• "By 3 minutes I have urgent obstetric review at the bedside and theatre alerted. By 5 minutes, if there is no recovery and no reversible cause corrected, I am moving to theatre while resuscitation continues. If the rate recovers up to about 9 minutes I reassess the whole picture; if it does not, we deliver by category 1 caesarean, because at 5 cm operative vaginal birth is not an option."^[2][1]
• "Paired umbilical cord gases at birth, neonatal team present, and a documented sequence of what I saw, what I did and who I told."^[2]

Probe 6 — communication. "She is asking whether her baby is alright."

Three of the eight domains are rapport, respect and communication. Demonstrate them out loud. ^[2]

• Sit at her eye level, use her name, and say something true and plain: "Your baby's heartbeat is showing a pattern we are not happy with. It does not mean something has gone wrong, but it means we need to act now rather than wait."
• Name what you are doing as you do it: "I am turning you onto your side and turning off the drip that has been making the contractions stronger, because that usually helps."
• Give her the next step and the timeframe: "I am asking my consultant to come now. If the pattern does not settle in the next few minutes, we will recommend a caesarean, and I will explain exactly what that involves before we move."
• Include her support person, allocate a staff member to stay with them, avoid jargon, and commit to a debrief afterwards.^[2]

Probe 7 — "Justify continuous monitoring at all. She wanted to stay mobile."

• "Continuous CTG halves neonatal seizures compared with intermittent auscultation — risk ratio 0.50 — but it does not reduce cerebral palsy or perinatal death, and it increases caesarean and instrumental birth."^[3]
• "She has induction and oxytocin, so the ANZ guideline recommends continuous monitoring. That recommendation is a conversation, not an order: I would explain both sides, and offer telemetry so she can keep moving if we have it."^[2][3]
• "If she declined, I would document the discussion, involve my consultant, offer the safest achievable alternative, and keep revisiting it rather than treating the refusal as final."^[2]