There are several maneuvers the Ob/Gyn can utilize in delivering a child with shoulder dystocia, including the McRobert’s.
Upon encountering a shoulder dystocia, immediately announce the condition, summon help, and alert the anesthesia department. Reassessment of risk factors is then called for. Since shoulder dystocia is a bone-to-bone apposition of the maternal symphysis pubis and the fetal shoulder, with opposing force vectors at right angles, increased traction on the fetal head will only increase the fetal shoulder’s impaction while stretching the fragile brachial plexus.
Instead, physicians should concentrate applied force at the shoulder girdle—either to rotate it or dislodge it directly. Primarily, this force should be directed straight downward, though transverse pressure may facilitate the shoulder’s movement into an oblique diameter of the pelvis.11-12
Note that if the fetal shoulders are inadequately rotated, normal downward traction may lead to injury, while traction directed along the brachial plexus may result in its stretching or avulsion (see SIDEBAR).
Do not administer fundal pressure as it tends to aggravate the shoulder impaction by further forcing the fetal shoulder against the maternal symphysis.
There are several clinical maneuvers the Ob/Gyn can utilize in delivering a child with shoulder dystocia. We’ve found the following sequence to be efficacious in our practice. As previously noted, this procedure should be well rehearsed and familiar to all labor and delivery personnel.
McRobert’s maneuver. Once extra assistants have arrived, perform the McRobert’s maneuver by flexing the fetal legs upward toward the mother’s abdomen. Then, apply gentle and continuous downward traction to the fetal head. Please note that the gentle application of traction will not increase fetal shoulder impaction. If the shoulder girdle remains impacted, cut a generous episiotomy. Now, as the mother pushes, again administer gentle and continuous downward traction to the fetal head. If the shoulder still remains impacted, direct an experienced assistant to apply suprapubic pressure. Note that fundal pressure should not be administered, as it tends to aggravate the impaction by further forcing the fetal shoulder against the maternal symphysis.
If further intervention is required, 2 maneuvers are available to decrease the functional length of the shoulder girdle.
Wood’s-corkscrew maneuver. To perform this technique, used in combination with maternal expulsion,13 rotate the anterior fetal shoulder toward the fetal sternum to dislodge the shoulder from the maternal symphysis. This should move the anterior shoulder to the posterior position and allow the impacted shoulder to slip under the symphysis. Apply gentle and continuous downward traction to the fetal head in conjunction with maternal pushing to effect delivery.
Direct delivery of the posterior shoulder.14 This maneuver should not to be performed in conjunction with maternal expulsive efforts or uterine contractions. Start by inserting a hand posterio-laterally to the pelvic outlet. Then, to gain more room in which the impacted anterior shoulder can be rotated, deliver the posterior arm by sweeping it anteriorly across the chest. This allows the impacted shoulder to drop behind the symphysis, completing fetal expulsion. Note, however, that even when this method is employed properly, the humerus may sustain injury.
Repeat the previously cited maneuvers as necessary. If all of the above strategies fail, more extreme measures may be needed.
Zavenelli maneuver. Here, the fetal head is pushed back into the vagina and an emergency cesarean section is performed. Combining vaginal and abdominal approaches may effect delivery.15-16 Unfortunately, at this point, the risk of neonatal morbidity and mortality is dramatically increased.
Symphysectomy. Another option is the symphysectomy procedure, in which the ligaments joining the symphysis are severed on their anterior aspect.17 Releasing these ligaments disrupts the pelvic girdle and increases its functional diameters so that delivery can be completed. Risks involved in this procedure include urethral trauma and orthopedic compromise postpartum.
One sequela of shoulder dystocia: brachial plexus injury
The brachial plexus is formed by the anterior rami of spinal segments C5, C6, C7, C8, and T1. Three cords—lateral, medial, and posterior—are formed as a result of the intermingling of these segmental spinal fibers and make up the peripheral nerves of the upper extremity.
In 1872, Duchenne was the first to associate injury to the brachial plexus due to traumatic delivery of the shoulder girdle. Two years later, Erb further clarified brachial plexus injury as it relates to shoulder girdle impaction, describing localized trauma to the fifth and sixth cervical nerve roots.1 Erb’s palsy—the most common brachial plexus injury—compromises the uppermost trunk, formed from spinal segments C5, C6, and C7. The resulting dysfunction manifests in the posture of the upper arm, the position of the scapula, and the attitude of the wrist. (Though Phrenic nerve involvement—C4 spinal segment—with resultant paralysis of the diaphragm has been described in conjunction with Erb’s palsy, it is very rare.)
Klumpke’s palsy, meanwhile, primarily affects the forearm and wrist. It is the direct result of injury to the lower trunk, which is comprised of nerve input from spinal segments C8 and T1. Flexion at the elbow accompanied by supination at the forearm results in the classic claw-like deformity of the hand. If the sympathetic fibers of T1 are affected, Horner’s syndrome may result.
REFERENCE
1. Swaiman KF, Wright FS. The Practice of Pediatric Neurology. 2nd ed. St. Louis, Mo: CV Mosby; 1982.