Skip to main content

Abnormal labour: dystocia, arrest, and the decisions that follow

Obstetrics

Power, passenger, passage. The definitions of arrest are precise and generous with time, because most slow labours end vaginally if they are allowed to.

Maternal

Contractions
strength and frequency, palpated and on the toco
Cervix
dilatation, effacement, station, position, caput and moulding
Hydration, pain, bladder, exhaustion
Hydration, pain, bladder, exhaustion
Oxytocin titrated to contractions, not to the clock
Oxytocin titrated to contractions, not to the clock

Fetal

Heart rate and its response to the augmented contractions
Heart rate and its response to the augmented contractions
Position of the occiput by sutures and fontanelles
Position of the occiput by sutures and fontanelles
Descent by station and by abdominal fifths
Descent by station and by abdominal fifths
Caput and moulding as the record of the fit
Caput and moulding as the record of the fit

Arrest, defined (ACOG/SMFM 2014)

SituationDefinition
Latent phaseProlonged latent phase (over 20 hours nulliparous, 14 multiparous) is not an indication for caesarean.
First-stage arrestAt 6 cm or more with ruptured membranes: no cervical change for 4 hours of adequate contractions, or 6 hours of inadequate contractions with oxytocin.
Second-stage arrestNo descent or rotation after 3 hours of pushing (nulliparous) or 2 hours (multiparous), longer with an epidural, provided the fetus is well.

The three Ps

PowerPassengerPassage
Contractions inadequate in frequency, duration or strength (Montevideo units under 200 on an intrauterine catheter)Occiput posterior or transverse, deflexed head, macrosomia, brow or face presentationCephalopelvic disproportion, rarely a contracted pelvis; a full bladder
Oxytocin augmentation; amniotomyPosition changes; manual rotation; time; operative delivery if the criteria are metEmpty the bladder; the diagnosis of true disproportion is made by failure to progress despite adequate contractions

Operative vaginal delivery and caesarean

  • Vacuum or forceps: full dilatation, ruptured membranes, engaged head at station plus 2 or lower, known position, adequate analgesia, empty bladder, an operator who can abandon and proceed to caesarean. Indications: prolonged second stage, fetal compromise, maternal exhaustion or a condition where pushing is unwise.
  • Caesarean for arrest is a diagnosis made after time and augmentation, not at the first slow hour. Category (urgency) is communicated clearly: immediate threat to life, maternal or fetal compromise that is not immediately life-threatening, no compromise but early delivery needed, at a time to suit.
  • Trial of labour after caesarean: appropriate for most with one prior low transverse incision; success around 60 to 80 percent; uterine rupture risk about 0.5 to 1 percent, higher with induction. Continuous monitoring; a sudden fetal bradycardia is rupture until proven otherwise.

Spinal for caesarean: the anaesthesia simulation in SurgSpace

Check

G1, 7 cm for 3 hours with membranes ruptured and contractions every 5 minutes lasting 40 seconds. Fetal heart rate Category I. What is the next step?

Watch it done

Intrapartum fetal surveillanceAPGO on YouTube

Association of Professors of Gynecology and Obstetrics teaching topic on reading the strip in labour.

Primary vertex caesarean sectionTVASurg, University of Toronto on YouTube

Layer by layer from skin to uterus and back, the sequence the operation note follows.

On the modelCervixBony pelvisIsthmus and lower segment

Frameworks and sources

  • ACOG / SMFM: Obstetric Care Consensus 1: safe prevention of the primary cesarean delivery (contemporary labour curves) (2014). Labour progress is taught from contemporary data (Zhang), not the older Friedman curve.

Content reviewed 2026-09. Teaching material for students, not clinical decision support; check the current edition of the guideline your unit uses.