Induction of labour — structured SAQ (15 marks)

(a) Bishop score with working (4 marks)

Two marks for the correct component scores, one for the total, one for the interpretation. ^[1][2]

• Total 3 of a maximum 13. Dilatation, effacement and station each score 0 to 3; consistency and position each score 0 to 2 — which is why the maximum is 13, not 15.^[1][2]
• Interpretation: markedly unfavourable. A score of 6 or less means cervical ripening is required before amniotomy and oxytocin; a score of 8 or more predicts a vaginal birth rate approaching that of spontaneous labour.^[2]

(b) Risks specific to this woman (4 marks)

One mark each, maximum four. Numbers earn the marks; "increased risk" does not. ^[3]

• Uterine rupture. In Lydon-Rochelle's population cohort of 20 095 women with one previous caesarean, rupture occurred at 1.6 per 1000 with elective repeat caesarean, 5.2 per 1000 with spontaneous labour, 7.7 per 1000 with induction not using prostaglandins, and 24.5 per 1000 with prostaglandin-induced labour (relative risk 15.6 versus repeat caesarean without labour). RANZCOG C-Obs 22 quotes rupture rates of 1.4 to 2.45 percent with prostaglandin induction after caesarean.^[3]
• The prostaglandin exclusion. RANZCOG C-Obs 22 states prostaglandins are generally not recommended after previous caesarean with a live fetus; they may be used for fetal death or termination of pregnancy.^[3]
• Emergency caesarean. Induction with an unfavourable cervix carries a higher chance of intrapartum caesarean than spontaneous labour, particularly after a previous caesarean at full dilatation.^[4]
• Tachysystole and fetal compromise, and the need for continuous cardiotocographic monitoring and intravenous access throughout.^[8]
• The alternatives she must hear: expectant management with surveillance, and elective repeat caesarean. RANZCOG C-Obs 38 governs the wider birth-after-caesarean conversation.^[4][9]

(c) Method, reasoning and regimen (5 marks)

One mark for the method with reasoning; three for the regimen detail; one for the safety framework. ^[5][7]

• Method: transcervical balloon catheter. Mechanical ripening achieves comparable vaginal birth rates to prostaglandin with less uterine hyperstimulation, which is exactly what a scarred uterus needs. Prostaglandin is avoided for the reasons in part (b).^[5][6]
• Balloon detail: single or double balloon passed through the cervix and inflated above the internal os — Queensland Clinical Guidelines specify 80 mL in each balloon of a double-balloon device, 80 mL for a single balloon, or 30 to 50 mL for a Foley catheter; NSW specifies typically 30 mL for a single balloon and 50 to 80 mL for a double balloon. Reassess at 12 hours with a plan for amniotomy; do not leave a balloon in situ beyond 18 hours.^[5]
• Then amniotomy once the cervix allows and the head is applied, followed by an oxytocin infusion.^[7]
• Oxytocin 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. Start at 1 milliunit per minute, increase no more often than every 30 minutes through the ladder 1, 2, 4, 8, 12, 16, 20, 24, 28, 32, aiming for 3 to 4 contractions in 10 minutes lasting 40 to 60 seconds with a rest period of not less than 60 seconds. Queensland caps at 32 milliunits per minute with obstetric review before exceeding 20; NSW caps at 20 milliunits per minute and calls anything higher off-label. With a uterine scar, cap at 20 milliunits per minute.^[7]
• Safety framework: continuous cardiotocography from the start of oxytocin, intravenous access, one-to-one midwifery care, a documented consultant decision, and birth in a unit with immediate theatre access.^[4][8]

(d) Hyperstimulation with an abnormal trace (2 marks)

• Stop the oxytocin immediately, turn her full left lateral, give an intravenous fluid bolus through a new administration set, and perform a vaginal examination to assess progress and exclude cord prolapse.^[8]
• Give acute tocolysis: terbutaline 250 micrograms subcutaneously or intravenously (alternatives in ANZ practice are salbutamol 100 micrograms intravenously or glyceryl trinitrate spray 400 micrograms sublingually). Call for senior help and prepare for birth, keeping uterine rupture actively in mind given her scar.^[8][3]