About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Incidence: ~0.6–0.7% of vaginal deliveries. Unpredictable — 50% occur with normal-weight babies
- Risk factors: fetal macrosomia (>4 kg), GDM, maternal obesity, previous shoulder dystocia, prolonged 2nd stage, instrumental delivery
- Recognised by: head delivers but retracts against perineum ("turtle sign"), failure of restitution
- First-line manoeuvres: McRoberts position (hyperflexion of hips) + suprapubic pressure (NOT fundal pressure)
- Second-line: episiotomy, delivery of posterior arm, internal rotational manoeuvres (Rubin II, Woods screw)
- Complications: Erb palsy (C5–C6 brachial plexus injury), fetal fractures, fetal hypoxia/death, maternal PPH and 3rd/4th degree tears
Overview
Shoulder dystocia is defined as a vaginal cephalic delivery that requires additional obstetric manoeuvres to deliver the fetal shoulders after gentle downward traction has failed. It occurs when the anterior fetal shoulder becomes impacted behind the maternal pubic symphysis (or rarely, the posterior shoulder on the sacral promontory). It is an obstetric emergency with a very narrow time window — delay increases the risk of fetal hypoxia and brachial plexus injury. Despite known risk factors, shoulder dystocia is largely unpredictable, occurring in approximately half of cases without any identifiable risk factor.
Epidemiology
Shoulder dystocia complicates approximately 0.6–0.7% of vaginal deliveries. The risk increases with increasing birth weight: ~1% for babies 3.5–4 kg, ~5% for babies 4–4.5 kg, and ~10–20% for babies >4.5 kg. However, approximately 50% of shoulder dystocias occur in babies of normal weight. Risk factors include fetal macrosomia, gestational or pre-existing diabetes, maternal obesity, previous shoulder dystocia (recurrence risk ~10–15%), prolonged second stage, and instrumental delivery.
Clinical Features
Symptoms
Head delivers but immediately retracts against the perineum — "turtle sign"
Failure of restitution (head does not rotate externally after delivery)
Shoulders fail to deliver with normal gentle traction
Signs
Turtle sign: delivered head retracting tightly against perineum
No delivery of anterior shoulder despite gentle downward traction
Cord compression may lead to rapidly deteriorating fetal heart rate
Investigations
First-line
Clinical recognitionDiagnosis is clinical — immediate recognition and action are paramount
Neonatal assessmentAfter delivery: check for brachial plexus injury (Erb palsy — limp arm in "waiter's tip" position), fractures (clavicle, humerus), Apgar scores
Second-line
Maternal assessmentCheck for perineal tears (3rd/4th degree), blood loss (PPH), urinary retention
Specialist
Neonatal imagingX-ray if fracture suspected. MRI/EMG for brachial plexus injury assessment
1
HELPERR mnemonic
- H — Help: call for senior obstetrician, second midwife, neonatal team, anaesthetist
- E — Evaluate for episiotomy: does NOT relieve bony impaction but creates space for manoeuvres
- L — Legs: McRoberts position (hyperflexion of maternal thighs onto abdomen). Straightens sacrum and increases AP diameter. FIRST MANOEUVRE
- P — suprapubic Pressure: applied by assistant behind the anterior shoulder (towards fetal chest) to dislodge from symphysis. Do this WITH McRoberts. NEVER apply fundal pressure
- E — Enter vagina for rotational manoeuvres: Rubin II (pressure on anterior aspect of posterior shoulder) or Woods screw (rotate shoulders 180°)
- R — Remove the posterior arm: reach in, grasp fetal forearm, sweep across chest and deliver
- R — Roll the patient: all-fours position (Gaskin manoeuvre) — increases pelvic dimensions
2
If all above fail (rare)
- Zavanelli manoeuvre: replace head into vagina and deliver by emergency CS (last resort)
- Symphysiotomy: surgical division of symphysis pubis (extremely rare in UK)
- Deliberate clavicular fracture (intentional to reduce shoulder diameter — controversial)
3
Post-delivery
- Cord blood gas analysis
- Thorough neonatal examination: brachial plexus, fractures, hypoxic injury
- Maternal examination: perineal trauma, PPH
- Document in detail: time of head delivery, manoeuvres performed and in which order, time of body delivery, cord gases, Apgar scores
- Debrief parents. Incident reporting and multidisciplinary review
Complications
- Erb palsy (C5–C6): Arm hangs limply in "waiter's tip" position (adducted, internally rotated, extended elbow, pronated forearm). Most recover spontaneously within 12 months. ~10% permanent
- Klumpke palsy (C8–T1): Rare — claw hand deformity
- Fetal fractures: Clavicle (most common — usually heals well) or humerus
- Fetal hypoxia and death: From cord compression — risk increases with head-to-body delivery interval
- Maternal: PPH, 3rd/4th degree perineal tears, psychological trauma
UKMLA Exam Tips
- 1Turtle sign = shoulder dystocia. Call for help immediately
- 2McRoberts + suprapubic pressure = FIRST manoeuvres. Resolves ~90% of cases
- 3NEVER apply fundal pressure — increases impaction and risk of uterine rupture
- 4Erb palsy (C5–C6): waiter's tip position. Most recover. Classic exam question
- 5Head-to-body delivery time: aim <5 minutes to avoid hypoxic injury
- 6Previous shoulder dystocia: ~10–15% recurrence risk. Counsel about delivery options
- 7HELPERR mnemonic is essential to know for exams and for clinical practice
practicetest your knowledge on shoulder dystociaApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — obstetrics and beyond.
open q-bank