Slow progress in labour and augmentation — structured SAQ (15 marks)

(a) Definition and classification (4 marks)

One mark for the definition, one for naming the guideline, two for a complete framework with examples. ^[1][2]

• Definition: RANZCOG C-Obs 31 defines slow labour by consensus as less than a 2 cm increase in cervical dilatation in a 4-hour period from 5 cm dilatation, adding that descent, rotation and application of the head also inform the diagnosis. She has gained 1 cm in 4 hours from 5 cm, so she meets it.^[1]
• Framework — power, passenger, passage:
  • Power: infrequent, short or weak contractions; loss of fundal dominance; exhaustion, dehydration, ketosis, a full bladder, unrelieved pain, infection. This woman has two of these already.^[1][7]
  • Passenger: occiput-posterior or transverse position, deflexion, asynclitism, macrosomia, and the rare malpresentations.^[2]
  • Passage: bony pelvic architecture, soft-tissue resistance, a full bladder or loaded rectum; true cephalopelvic disproportion is rare without a distorted pelvis.^[1]
• State the trap: she is a nullipara with an epidural, so a slower active phase is expected; and the epidural effect is not dystocia.^[2]

(b) Reassessment and pre-oxytocin measures (4 marks)

One mark per group. Marks are lost for going straight to a drug. ^[6][7]

• The woman: catheterise the bladder (five hours without voiding with an epidural in situ); assess and improve analgesia; correct dehydration and ketosis with oral intake or intravenous fluid; check temperature, pulse and exhaustion.^[1][7]
• The labour: palpate contractions by hand for a full 10 minutes — the tocograph gives frequency, not strength; abdominal palpation for fifths palpable; vaginal examination for dilatation, effacement, station, position by sagittal suture and fontanelles, caput and moulding graded, and cervical application.^[1]
• The environment: restore continuous one-to-one support, and encourage upright positions and mobility — both change outcomes, and cost nothing. Upright positions and mobility in the first stage shorten labour and are associated with fewer caesareans; continuous support increases spontaneous vaginal birth (RR 1.08) and reduces caesarean birth (RR 0.75).^[6][7]
• Amniotomy, deliberately: RANZCOG C-Obs 31 advises that amniotomy should not be performed routinely and that combined early amniotomy with oxytocin should not be used routinely; in slow labour with intact membranes it may be considered after explaining that the effect on labour length and mode of birth is uncertain.^[1][5]
• Say the honest benefit before you prescribe: oxytocin shortens labour by about two hours and does not reduce caesarean birth.^[3]

(c) The oxytocin regimen and the reassessment criterion (5 marks)

Two marks for a complete regimen, one for the target, one for the ceiling, one for a stated reassessment criterion with a timing. ^[4]

• Continuous cardiotocography from the start of the infusion, contraction frequency counted by palpation, and one-to-one midwifery care.^[8]
• Reassessment criterion: vaginal examination 4 hours after the infusion has produced regular adequate contractions. If dilatation has increased by less than 2 cm, this needs obstetric review and a decision about caesarean birth rather than another increment; if 2 cm or more, continue with 4-hourly examinations.^[1][4]
• High dose versus low dose: the Cochrane review of high-dose (starting dose and increments of 4 milliunits per minute or more) versus low-dose regimens found shorter labour and lower caesarean rates, but the differences vanished on sensitivity analysis and the authors concluded there is insufficient evidence to recommend high-dose regimens routinely.^[4]

(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. Call for senior help.^[8]
• Give acute tocolysis: terbutaline 250 micrograms subcutaneously or intravenously (ANZ alternatives are salbutamol 100 micrograms intravenously or glyceryl trinitrate spray 400 micrograms sublingually), and prepare for birth if the trace does not recover.^[8]