Shoulder dystocia occurs during an attempted vaginal delivery (in the second stage of labor [pushing]) when the fetal head delivers but delivery does not progress because the anterior shoulder is impacted behind the pubic symphysis or the posterior shoulder is obstructed by the sacral promontory. It is an obstetric emergency and may result in fetal injury or death or maternal injury.
Shoulder dystocia is an obstetric emergency that occurs in approximately 0.2% to 3.0% of vaginal deliveries (with a vertex fetal presentation) (1). Risk factors for shoulder dystocia should be noted during prenatal care and, if a patient is at increased risk, preparations should be made for a potential shoulder dystocia. If the risk is very high, a planned cesarean delivery may be appropriate.
General reference
1. Practice Bulletin No 178: Shoulder Dystocia. Obstetrics & Gynecology 129(5):p e123-e133, 2017. doi: 10.1097/AOG.0000000000002043
Risk Factors of Shoulder Dystocia
Risk factors include
Maternal obesity
Shoulder dystocia in a previous pregnancy
Rapid labor
Risk of neonatal morbidity (eg, brachial plexus injury, bone fractures) and mortality is increased. Maternal morbidity may include postpartum hemorrhage, perineal lacerations, sphincter injuries, symphysis pubis separation, and lateral femoral cutaneous neuropathy associated with hyperflexion of the legs.
Fetopelvic disproportion is suggested by prenatal clinical estimates of pelvic dimensions, ultrasonography, and protracted labor.
Signs and Symptoms of Shoulder Dystocia
An early sign of a potential shoulder dystocia is a protracted second stage of labor, particularly in a fetus with risk factors.
If a large fetus is suspected (> 4000 g) and the progress of labor is protracted, the obstetric team should prepare for a potential shoulder dystocia.
Diagnosis of Shoulder Dystocia
Shoulder dystocia is diagnosed when the fetal head is delivered but then retracts against the maternal perineum (turtle sign) and then the anterior shoulder does not deliver despite gentle, downward traction on the fetal head.
Management of Shoulder Dystocia
Announce to the clinical team that there is a shoulder dystocia and call for additional obstetrics, pediatrics, and anesthesiology staff, as needed.
Position pregnant patient in dorsal lithotomy.
Perform maneuvers (McRoberts, suprapubic pressure, Wood screw, Rubin, delivery of posterior shoulder or arm).
Sometimes, intentionally fracture the fetal clavicle.
If all other measures fail, perform the Zavanelli maneuver (flexion and replacement of fetal head into the maternal pelvis followed by cesarean delivery).
< 5000 g in women without diabetes or < 4500 g in women with diabetes, labor may safely continue. Patients may also be evaluated to determine whether operative vaginal delivery (by forceps or vacuum extractor) is safe and appropriate. However, trying to deliver a fetus that is too large using forceps or a vacuum extractor can cause complications.
Once shoulder dystocia is recognized, extra personnel are summoned to the room, and various maneuvers are tried sequentially to disengage the anterior shoulder:
The woman’s thighs are hyperflexed to widen the pelvic outlet (McRoberts maneuver), and suprapubic pressure is applied to rotate and dislodge the anterior shoulder. Fundal pressure is avoided because it may worsen the condition or cause uterine rupture.
The obstetrician inserts a hand into the posterior vagina and presses the posterior or anterior shoulder to rotate the fetus in whichever direction is easier (Wood screw maneuver or Rubin maneuver).
The obstetrician inserts a hand, flexes the posterior elbow, and sweeps the arm and hand across the fetal chest to deliver the infant’s entire posterior arm.
If the obstetrician cannot reach the posterior arm, axillary traction may be used (by placing fingers in the posterior axilla) to attempt to deliver the posterior shoulder.
An episiotomy can be done at any time to facilitate the maneuvers. Sometimes, if other maneuvers are not effective, clinicians help the patient turn over and get into all-fours position (on hands and knees; Gaskin maneuver), although this is considered an option of last resort (1).
These maneuvers increase risk of fracture of the humerus or clavicle. Sometimes the clavicle is intentionally fractured in a direction away from fetal lung to disengage the shoulder.
If all maneuvers are ineffective, the obstetrician flexes the infant’s head and reverses the cardinal movements of labor, replacing the fetal head back into the vagina or uterus (Zavanelli maneuver); the infant is then delivered by cesarean. In settings where safe and rapid cesarean delivery is not possible, symphysiotomy (widening the pelvic outlet by surgically incising the cartilage of the pubic symphysis) may be considered. This procedure is used rarely because it results a high risk of long-term maternal morbidity, including obstetric fistulae and urinary incontinence (2).
Management references
1. Lau SL, Sin WTA, Wong L, et al: A critical evaluation of the external and internal maneuvers for resolution of shoulder dystocia. Am J Obstet Gynecol Published online August 17, 2023. doi:10.1016/j.ajog.2023.01.016
2. Wilson A, Truchanowicz EG, Elmoghazy D, et al: Symphysiotomy for obstructed labour: a systematic review and meta-analysis. BJOG 123(9):1453-1461, 2016. doi:10.1111/1471-0528.14040
Key Points
Prepare for shoulder dystocia if a large fetus is suspected (> 4000 g), and the progress of labor is protracted.
If shoulder dystocia occurs, call extra personnel to the delivery room.
Try various maneuvers sequentially to disengage the anterior shoulder.
If these maneuvers are unsuccessful, place the fetal head back into the vagina or uterus and deliver the infant by cesarean.
