From the Editor

Tackle the challenging shoulder dystocia emergency by practicing delivery of the posterior arm

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Successful delivery of the posterior arm may require finding and firmly grasping the fetal hand, wrist, and/or distal forearm


 

References

CASE: McRobert’s maneuver fails
You are attempting an early term vaginal delivery of a 31-year-old G2P1 woman with type 2 diabetes mellitus and an estimated fetal weight of 4,100 g. The fetal head has delivered but retracted against the perineum, producing the “turtle sign.”

You call a shoulder dystocia emergency and request help. In sequence, you tell the mother to stop pushing, check for a nuchal cord, and cut a mediolateral episiotomy. Working seamlessly with your nurse, you place the patient at the edge of the bed, perform the McRobert’s maneuver, provide suprapubic pressure and apply gentle downward guidance to the fetal head. Unfortunately, with these maneuvers the baby does not deliver.

What is your next obstetric maneuver?

With alacrity, move on to an advanced maneuver. In this article, I outline your options for this advanced maneuver and describe the technique for execution. First, however, I discuss the amount of time you have to work with.

How long do you have to perform advanced maneuvers?
In managing a difficult shoulder dystocia, critical goals are to avoid permanent injury to the newborn, including brachial plexus injury, fetal asphyxia, central nervous system injury, and death. Many experts believe that the accoucheur has approximately 4 or 5 minutes to deliver the impacted fetus before the risk of these adverse outcomes rises substantially.1-3 In one study, a head-to-body delivery interval of less than 5 minutes and 5 minutes or longer were associated with rates of hypoxic ischemic encephalopathy of 0.5% and 24%, respectively.2

Stay calm, move on. Given the time pressure for management, it is important to initiate an advanced maneuver, such as rotation of the fetal body or delivery of the posterior arm, when the initial sequence of McRobert’s maneuver, suprapubic pressure, and gentle downward guidance on the fetal head do not result in delivery. Repetitively repeating these initial maneuvers will increase the risk of an adverse fetal outcome. Stay calm and quickly move on to an advanced maneuver.

Advanced maneuvers
The two advanced shoulder dystocia maneuvers that often result in a successful birth are:

  • rotation of the fetal shoulders
  • delivery of the posterior arm.4,5

In a prior editorial, I described in detail the Woods and Rubin rotational maneuvers.6 In this editorial, I focus on the technique for delivery of the posterior arm.

Delivery of the posterior arm
This maneuver to resolve difficult shoulder dystocia deliveries has been in the armamentarium of obstetricians since at least the mid-18th Century.7 The delivery of the posterior arm reduces the presenting fetal diameter from the larger bisacromial diameter to the smaller axilloacromial diameter. Experts estimate that this change results in a 2-cm decrease in the presenting fetal diameter, thereby facilitating delivery.8,9

In describing posterior arm delivery, it is important to clearly define the anatomy of the upper extremity. The arm is the portion of the upper extremity from the shoulder to the elbow joint. The long bone of the arm is the humerus. The forearm is the portion of the upper extremity from the elbow to the wrist. The long bones of the forearm are the radius and ulna.

Descriptions of how to deliver the posterior arm range from concise to detailed. A concise description recommends “inserting a hand in the vagina, grasping the fetal arm, and sweeping it across the chest.”9

These detailed instructions are provided by Dr. John Rodis, Chief of Obstetrics and Gynecology at St. Francis Hospital in Hartford Connecticut, in UpToDate:

Introduce a hand into the vagina to locate the posterior shoulder and arm. If the fetal abdomen faces the maternal right, the operator’s left hand should be used; if the fetal abdomen faces the maternal left, the right hand is used. The posterior arm should be identified and followed to the elbow. If the elbow is flexed, the operator can grasp the forearm and hand and pull out the arm. If it is extended, pressure is applied in the antecubital fossa. This flexes the elbow across the fetal chest and allows the forearm or hand to be grasped. The arm is then pulled out of the vagina, which brings the posterior shoulder out of the pelvis and reduces the shoulder diameter by 2 to 3 cm. If the anterior shoulder cannot be delivered at this point, the fetus can be rotated and the procedure repeated for the anterior (now posterior) arm.10

Additional technical guidance. After grasping the fetal wrist and hand, pull the upper extremity against the fetal chest. Approaching the vaginal introitus, pull the wrist and hand toward the fetal ear nearest the maternal symphysis pubis.11 These maneuvers may result in a fracture to the humerus, but this complication is acceptable given the risk of fetal asphyxia and death.

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