Residency · Residency · Obstetrics Gynecology
Shoulder Dystocia: Prevention, Recognition, and Management
Definition
Shoulder dystocia is the failure of the fetal shoulders to deliver spontaneously after delivery of the fetal head. It is formally defined as a delivery requiring additional obstetric maneuvers beyond gentle downward traction. An alternative definition uses a head-to-body delivery time exceeding 60 seconds. In most cases, the anterior shoulder is impacted behind the maternal pubic symphysis. Less commonly, the posterior shoulder is impacted on the sacral promontory, a situation referred to as bilateral shoulder dystocia.
Epidemiology
Shoulder dystocia complicates 0.2 to 3% of vaginal deliveries, with the range reflecting differences in population and definition. The incidence is higher with macrosomia and maternal diabetes. Notably, approximately 50% of shoulder dystocia cases occur in infants weighing less than 4,000 g, and no reliable screening tool exists to predict this complication.
Risk Factors
Antepartum
Antepartum risk factors include fetal macrosomia with an estimated fetal weight above 4,000 g, with the risk increasing significantly above 4,500 g. Maternal diabetes is a particularly important risk factor because macrosomic infants of diabetic mothers have larger shoulder-to-head ratios. Additional antepartum risk factors include maternal obesity, excessive gestational weight gain, a history of prior shoulder dystocia (with recurrence risk of 1 to 25%), post-term pregnancy, and multiparity with large prior infants.
Intrapartum
Intrapartum risk factors include prolonged first or second stage of labor, operative vaginal delivery with forceps or vacuum, oxytocin augmentation, precipitous delivery, and epidural anesthesia (which may indirectly contribute through prolonged pushing).
Limitations of Risk Factor Assessment
Most shoulder dystocia events occur in the absence of identifiable risk factors. No combination of risk factors has sufficient predictive value to prevent the majority of cases. Prophylactic cesarean for macrosomia alone is not recommended unless the estimated fetal weight is 5,000 g or greater in non-diabetic women or 4,500 g or greater in diabetic women.
<image>Diagram showing the mechanism of anterior shoulder dystocia, with the fetal anterior shoulder impacted behind the maternal pubic symphysis, the fetal head delivered and retracted against the perineum (turtle sign), and arrows indicating the direction of impaction</image>
Recognition
Signs of Shoulder Dystocia
The turtle sign is the hallmark finding: the fetal head delivers and then retracts tightly against the perineum. The head does not undergo restitution or external rotation. Gentle downward traction fails to deliver the anterior shoulder, and traction on the fetal head alone fails to deliver the body.
Immediate Actions Upon Recognition
When shoulder dystocia is recognized, help should be called immediately, including additional nurses, a second obstetrician, anesthesia, and pediatrics or NICU. The time should be noted and documented as the head delivery time for calculating the head-to-body interval. Excessive traction and fundal pressure must be avoided because they increase the risk of brachial plexus injury and uterine rupture. Clear, calm communication with the patient and team is essential.
Management Maneuvers
First-Line Maneuvers
McRoberts Maneuver
The McRoberts maneuver involves hyperflexion of the maternal hips, bringing the knees to the chest or axillae. This flattens the sacrum, rotates the symphysis cephalad, and increases the anteroposterior diameter of the pelvis. It requires no fetal manipulation and resolves 40 to 50% of shoulder dystocia cases when combined with suprapubic pressure. It should be the first maneuver attempted.
Suprapubic Pressure
Suprapubic pressure is applied by an assistant using the heel of the hand just above the symphysis. The pressure is directed downward and laterally, toward the fetal chest, to dislodge the anterior shoulder from behind the symphysis. A rocking motion may be effective. This maneuver is combined with McRoberts as part of the initial response. Fundal pressure must never be applied, as it drives the shoulder further into the pelvis.
Second-Line Maneuvers (Internal Rotational)
Rubin II Maneuver
The Rubin II maneuver involves inserting a hand into the vagina posteriorly and pushing the posterior aspect of the fetal anterior shoulder toward the fetal chest, adducting the shoulders. This reduces the bisacromial diameter. It is often combined with the Woods corkscrew maneuver.
Woods Screw Maneuver
In the Woods screw maneuver, fingers are placed on the anterior aspect of the fetal posterior shoulder. The posterior shoulder is then rotated 180 degrees anteriorly, like turning a screw, which replaces the anterior shoulder with the posterior shoulder. This can be combined with the Rubin II maneuver by simultaneously pushing the anterior shoulder forward while rotating the posterior shoulder.
Reverse Woods Screw
The reverse Woods screw rotates the posterior shoulder in the opposite direction and is attempted if the initial rotation fails.
Third-Line Maneuvers
Delivery of the Posterior Arm
To deliver the posterior arm, the hand enters the vagina and sweeps along the posterior arm to the fetal elbow. The elbow is flexed, and the forearm is swept across the fetal chest. The fetal hand or wrist is grasped, and the posterior arm is delivered. This reduces the bisacromial diameter by approximately 2 cm, the width of the arm. The success rate is high, ranging from 84 to 90%, and many experts consider it the most effective single maneuver. The primary risk is fetal humeral fracture, which heals well. Some experts advocate moving directly to posterior arm delivery after McRoberts and suprapubic pressure fail.
Gaskin Maneuver (All-Fours Position)
The Gaskin maneuver involves rolling the patient to a hands-and-knees position. Gravity and the change in pelvic dimensions may dislodge the shoulder. In the original description, it was effective in 83% of cases. However, it is difficult to perform in patients with an epidural and requires a cooperative patient.
| Maneuver | Line | Technique | Success Rate | Key Notes |
|---|---|---|---|---|
| McRoberts | First | Hyperflex maternal hips to chest | 40-50% (with suprapubic pressure) | Always attempt first; no fetal manipulation |
| Suprapubic pressure | First | Heel of hand above symphysis, downward/lateral | Combined with McRoberts | Never apply fundal pressure |
| Rubin II | Second | Push posterior aspect of anterior shoulder toward fetal chest | Variable | Adducts and reduces bisacromial diameter |
| Woods screw | Second | Rotate posterior shoulder 180° anteriorly | Variable | Can combine with Rubin II |
| Delivery of posterior arm | Third | Flex fetal elbow, sweep forearm across chest | 84-90% | Most effective single maneuver; risk of humeral fracture |
| Gaskin (all-fours) | Third | Roll patient to hands-and-knees | 83% | Difficult with epidural |
| Zavanelli | Last resort | Replace fetal head, proceed to cesarean | Rare | Significant morbidity; uterine relaxation needed |
Last-Resort Maneuvers
Zavanelli Maneuver
The Zavanelli maneuver involves replacing the fetal head into the vaginal canal, reversing the cardinal movements by flexing the head, rotating to occiput anterior, and pushing back into the pelvis. This is followed by cesarean delivery. Terbutaline or nitroglycerin is administered for uterine relaxation. The maneuver is associated with significant neonatal morbidity and is rarely needed, reserved for complete failure of all other maneuvers.
Clavicle Fracture (Intentional)
Direct pressure on the mid-clavicle of the anterior shoulder can be applied to intentionally fracture it and reduce the bisacromial diameter. This is difficult to perform intentionally and carries a risk of underlying vascular or pulmonary injury.
Abdominal Rescue / Hysterotomy
Emergency cesarean with manual rotation of the shoulder from above while an assistant pushes from below is an extremely rare last resort.
<image>Sequential illustration of shoulder dystocia management maneuvers: (A) McRoberts maneuver with hyperflexed maternal hips, (B) suprapubic pressure applied by assistant, (C) Rubin II maneuver pushing anterior shoulder toward fetal chest, (D) delivery of the posterior arm with flexion of the fetal elbow</image>
Complications
Neonatal
Brachial plexus injury occurs in 4 to 16% of shoulder dystocia cases. Erb palsy, involving C5 and C6, is the most common form and presents with the classic waiter's tip position. It resolves within 12 months in 80 to 90% of cases. Klumpke palsy, involving C8 and T1, is rare and involves the hand and wrist. Total plexus injury has the worst prognosis. It is important to recognize that brachial plexus injury can occur without shoulder dystocia and even without excessive traction, as in utero forces can be responsible. Clavicle fracture occurs in 2 to 10% of cases and generally heals well without long-term sequelae. Humeral fracture, usually resulting from delivery of the posterior arm, also heals well. Hypoxic-ischemic encephalopathy risk increases when the head-to-body delivery time exceeds 5 minutes. Fetal death is rare but has been reported with prolonged entrapment.
Maternal
Maternal complications include postpartum hemorrhage in 11% of cases, third- or fourth-degree perineal laceration, cervical or vaginal lacerations, uterine rupture (rare, associated with excessive fundal pressure), and psychological trauma.
Documentation
Essential Elements
Documentation must include the time of head delivery and body delivery to calculate the head-to-body interval, the maneuvers performed and their sequence, personnel present and their roles, providers called and their response times, fetal position and estimated fetal weight, cord blood gases, neonatal assessment including Apgar scores and evidence of injury, and a detailed narrative note using specific terminology about the maneuvers performed.
What to Avoid in Documentation
Vague terms such as "moderate traction" should be avoided in favor of specific descriptions. "No excessive force" is subjective and unhelpful. Delayed or amended notes raise questions in litigation.
Simulation and Team Training
Shoulder dystocia drills should be conducted regularly, with quarterly frequency recommended. All team members, including obstetricians, midwives, nurses, and anesthesia providers, should participate. Structured debriefing is performed after each drill and after each real event. Two commonly used mnemonics guide the management sequence: HELPERR (Help, Evaluate for Episiotomy, Legs for McRoberts, suprapubic Pressure, Enter maneuvers for Rubin/Woods, Remove posterior arm, Roll for Gaskin) and ALARMER (Ask for help, Legs for McRoberts, Anterior shoulder pressure, Rotation, Manual delivery of posterior arm, Episiotomy, Roll to all fours).
Clinical Pearls
Shoulder dystocia is unpredictable, and most cases occur in non-macrosomic infants without identifiable risk factors.
McRoberts combined with suprapubic pressure should always be the first response and resolves approximately 50% of cases.
Fundal pressure must never be applied, as it worsens impaction and increases the risk of injury.
Delivery of the posterior arm is the most effective single maneuver and should be attempted early if initial maneuvers fail.
A head-to-body delivery time exceeding 5 minutes significantly increases the risk of hypoxic injury.
Brachial plexus injury can occur without excessive traction and even without clinically recognized shoulder dystocia.
Meticulous documentation is critical, as shoulder dystocia is one of the most litigated events in obstetrics.
Regular simulation drills improve team performance and reduce neonatal injury rates.
References
- ACOG Practice Bulletin No. 178: Shoulder Dystocia (2017, reaffirmed 2022)
- Gherman RB et al. Shoulder dystocia: the unpreventable obstetric emergency. Am J Obstet Gynecol. 2006;195:657-672
- Baxley EG, Gobbo RW. Shoulder dystocia. Am Fam Physician. 2004;69:1707-1714
- Leung TY et al. Head-to-body delivery interval and risk of fetal acidosis and hypoxic ischaemic encephalopathy. BJOG. 2011;118:474-479
- Crofts JF et al. Training for shoulder dystocia: a trial of simulation using low-fidelity and high-fidelity mannequins. Obstet Gynecol. 2006;108:1477-1485
