Induction of labour — structured oral station (12 minutes)

Opening prompt — "Can she start the oxytocin?"

Model response — answer the question, then justify: ^[2][3]

• "Not yet. RANZCOG C-Obs 22 states that oxytocin should not be used for 4 to 6 hours after the last prostaglandin dose. Her second dinoprostone gel was at 15:00, so the earliest I would start oxytocin is 21:00, and Queensland's operational rule of no oxytocin within 6 hours of gel would take that to 21:00 as well."
• "Before I start it, I want three things: a normal cardiotocograph, an assessment of whether the cervix will now allow amniotomy, and intravenous access."
• "Starting oxytocin inside the prostaglandin window stacks one myometrial stimulant on another. That is a classic, avoidable cause of hyperstimulation."^[2][4]

Examiner is listening for: the interval, the reason for the interval, and a plan rather than a refusal. ^[2]

Probe 1 — "Reproduce the Bishop score for me."

• "Five components. Dilatation, effacement, station, consistency and position. Dilatation, effacement and station each score 0 to 3; consistency and position each score 0 to 2. Maximum 13."^[1][2]
• "Dilatation: closed 0, 1 to 2 cm scores 1, 3 to 4 cm scores 2, 5 cm or more scores 3. Effacement: 0 to 30% scores 0, 40 to 50% scores 1, 60 to 70% scores 2, 80% or more scores 3. Station on the minus 3 to plus 3 scale: minus 3 scores 0, minus 2 scores 1, minus 1 or 0 scores 2, plus 1 or plus 2 scores 3. Consistency: firm 0, medium 1, soft 2. Position: posterior 0, mid 1, anterior 2."^[1][2]
• "6 or less is unfavourable and needs ripening; 8 or more predicts a vaginal birth rate approaching spontaneous labour."^[2]

Probe 2 — "She is now on oxytocin. Talk me through the regimen."

• "30 international units in 500 mL of compound sodium lactate or sodium chloride 0.9%, so that 1 mL per hour equals 1 milliunit per minute."^[3]
• "Start at 1 milliunit per minute. Increase no more often than every 30 minutes through 1, 2, 4, 8, 12, 16, 20, 24, 28, 32."^[3]
• "Target 3 to 4 contractions in 10 minutes, lasting 40 to 60 seconds, with a rest period of not less than 60 seconds — palpated, not read off the tocograph."^[3]
• "Queensland's ceiling is 32 milliunits per minute with obstetric review before exceeding 20; NSW caps at 20 and calls anything above it off-label. With a uterine scar I would cap at 20."^[3]
• "I would titrate to contractions, not to the clock: the Cochrane review of high-dose versus low-dose regimens found high-dose shortens labour but increases hyperstimulation without clearly improving caesarean or neonatal outcomes."^[3]

Probe 3 — "She is now contracting six times in ten minutes. What is that called, and what do you do?"

The examiner will press on the definition. Give it precisely, then split the management. ^[4]

• "Tachysystole — RANZCOG C-Obs 1 defines it as contractions in active labour at a rate greater than five in ten minutes without fetal heart rate abnormalities. Hypertonus is a contraction lasting more than two minutes with less than 60 seconds between contractions. Hyperstimulation is either pattern with fetal heart rate abnormalities."^[4]
• "If the trace is normal: reduce or stop the oxytocin, reposition her left lateral, give intravenous fluid, and observe. Excessive uterine activity without evidence of fetal compromise is not in itself an indication for tocolysis."^[4]
• "If the trace becomes abnormal, this is hyperstimulation: stop the oxytocin, remove any prostaglandin still in situ, reposition, fluid bolus, examine to exclude cord prolapse, and give terbutaline 250 micrograms subcutaneously or intravenously — alternatives in ANZ practice are salbutamol 100 micrograms intravenously or glyceryl trinitrate spray 400 micrograms sublingually. Call for help and prepare for birth if the trace does not recover."^[4]

Probe 4 — "It is now the following afternoon. She has had 14 hours of oxytocin with ruptured membranes and is 4 cm. She is exhausted and asking for a caesarean. What do you say and what do you do?"

Two domains at once: clinical knowledge and communication. Answer both. ^[5][6]

• The evidence first: "I would not call this a failed induction yet. In a secondary analysis of 1347 nulliparous inductions with an unfavourable cervix, 39.4% of women still in the latent phase after 12 hours of oxytocin and ruptured membranes went on to birth vaginally. In a separate cohort of 10 677 women, 96.4% had reached the active phase by 15 hours, and over 40% of those with a latent phase of 18 hours or more still had a vaginal birth."^[5][6]
• Then reassess: contractions palpated and adequate, oxytocin at an effective rate, bladder empty, pain relief adequate, position and station checked, cardiotocograph reviewed, and no sign of chorioamnionitis.^[5]
• Then talk to her, out loud: "You have worked incredibly hard and I am not going to pretend this has been quick. The good news is that your cervix has changed — you are 4 cm now. Most women in your position do get to a vaginal birth from here. What I would like to do is give you a proper epidural if you want one, keep the drip going, and reassess in a set time. If we get to that point and nothing has changed, we will talk about a caesarean and I will not argue with you. Is that a plan you can live with?"
• Name the safety line: "I would move to caesarean earlier than that if the fetal heart rate became abnormal, if she developed a fever, or if she made a fully informed request after that conversation."^[6]

Probe 5 — "Why was she being induced at 41+3 in the first place?"

• "Because the risk of stillbirth and severe neonatal morbidity rises after 41 weeks. The individual participant data meta-analysis of induction at 41 versus 42 weeks found severe adverse perinatal outcome in 0.4% versus 1.0% (relative risk 0.43, 95% CI 0.21 to 0.91; number needed to treat 175), with no difference in caesarean birth and the benefit concentrated in nulliparous women."^[7]
• "WHO recommends induction at or beyond 41+0 weeks and advises against routine induction before 41 weeks in an uncomplicated pregnancy. NICE frames it as a discussion from 41+0 weeks rather than an instruction."^[7][8]