Shoulder Dystocia
Steven L. Clark
Michael A. Belfort
GENERAL PRINCIPLES
DEFINITION
Shoulder dystocia refers to an impaction of the anterior shoulder of the fetus behind the pubic symphysis following delivery of the fetal head, preventing spontaneous delivery of the body. It is most commonly defined as a delivery that requires additional maneuvers following failure of gentle downward traction on the fetal head to effect delivery of the shoulders (1).
Because the umbilical cord is typically compressed between the fetal body and one or more bony pelvic prominences at this point in delivery, fetal hypoxia may rapidly follow.
If unrelieved, such hypoxia will result in fetal injury or death.
In addition, standard maneuvers utilized to relieve the shoulder dystocia may result in injury to the fetal brachial plexus, or, more rarely, the phrenic nerve.
Appropriate performance of these maneuvers will reduce, but not eliminate, such injuries. Thus, every clinician who delivers babies should be familiar with and capable of performing these maneuvers.
DIAGNOSIS
Shoulder dystocia is diagnosed when the standard degree of downward traction employed for vaginal delivery does not result in delivery of the anterior shoulder (1).
This condition may also be suspected before the application of any traction when retraction of the fetal head against the maternal perineum is observed (Turtle sign).
A proposed alternative definition involves a head-to-body delivery interval of 60 seconds or more.
Although this definition may have some value in achieving standardized, retrospective reporting of shoulder dystocia, it is not helpful to the clinician faced with this complication at the time of delivery.
Although it is not possible to objectively determine the allowable amount of traction that may be properly applied before moving to the special maneuvers described subsequently, experience will allow the clinician to judge when the force applied reaches the acceptable limits generally employed with uncomplicated deliveries.
RISK FACTORS
Multiple risk factors for shoulder dystocia have been identified. Unfortunately, most of these are common, nonspecific, and not helpful in clinical management.
Three risk factors, however, have sufficient predictive value to impact clinical management to avoid shoulder dystocia. In the presence of any of these risk factors, cesarean delivery should be considered to avoid shoulder dystocia.
Large for gestational age: The risk of shoulder dystocia is directly related to the weight of the fetus. The American College of Obstetricians and Gynecologists has recommended consideration of cesarean delivery for infants with an estimated weight of ≥5,000 g, or ≥4,500 g for an infant of a diabetic mother.
Midpelvic arrest of descent with an estimated fetal weight exceeding 4,000 g: Under such circumstances, cesarean delivery is preferred over operative vaginal delivery.
Previous shoulder dystocia: Although some authorities suggest that cesarean is indicated only if a previous shoulder dystocia resulted in permanent brachial plexus injury, others, including us, feel it unwise to attempt vaginal delivery after a prior shoulder dystocia event. Unless there is reason to believe that the infant will be significantly smaller than the previous child, many experts recommend cesarean delivery.
It is important to emphasize that most infants with shoulder dystocia will have none of these risk factors.
The mnemonic DOPE—diabetes, obesity, postmaturity, and excessive weight gain—is a useful checklist for remembering conditions of potential importance. All of these conditions may play into the risk factors mentioned earlier.
Procedures and Techniques
When a shoulder dystocia is diagnosed, a predetermined sequence of procedures should be initiated (2,3):
A call for additional assistance from nursing and anesthesiology; performance of the McRoberts maneuver; and application of suprapubic pressure, as described subsequently, are typically the first maneuvers employed.
The Woods/Rubin/raft and other shoulder displacement maneuvers, posterior hand/arm release, and episiotomy may be properly performed in any order, depending on the clinical judgment and experience of the delivering clinician.
The abdominal rescue and Zavanelli maneuver (cephalic replacement) are procedures of last resort.
Call for help.
Additional nurses may assist with the McRoberts maneuver and suprapubic pressure.
Anesthesiologist should prepare to initiate general anesthesia if the initial maneuvers are unsuccessful and/or additional maternal relaxation is necessary.
McRoberts Maneuver
This is performed by flexing the maternal thighs upon the abdomen (Tech Figure 4.5.1). This maneuver results in a change in the dimensions but not in the absolute size of the pelvic outlet via cephalad rotation of the symphysis pubis and a flattening of the sacrum (4).
This maneuver alone is effective in relieving up to 90% of cases of shoulder dystocia and should be maintained during performance of the additional maneuvers described later.
Suprapubic Pressure
This is often administered as a first-line maneuver by nursing staff in conjunction with the McRoberts maneuver.
It is performed by the application of firm oblique and downward pressure (i.e., from the posterior aspect of the impacted fetal shoulder) that will compress and rotate the anterior fetal shoulder under the symphysis.
By applying the vector of force toward the fetal face, there will be a flexion of the impacted shoulder toward the chest as an aid to displacing it under the pubic symphysis. We suggest this modification to the simple imparting of downward pressure, although no published evidence exists of improved outcomes with this refinement of the suprapubic pressure maneuver.
Rotational Maneuvers
Over the years, several rotational maneuvers have been described and variously defined for the relief of shoulder dystocia. These include the Woods maneuver, corkscrew maneuver, Rubin maneuver, and Raft maneuver, along with various modifications of each. However there is no generally accepted “bright line” between the definition of any of these maneuvers and the associated terminology can be confusing. Each of these maneuvers has in common attempts by the delivering clinician to rotate the fetal shoulders by placing the fingers behind or in front of the anterior or posterior shoulder and then applying rotational pressure in conjunction with ongoing suprapubic pressure (Tech Figure 4.5.2). The delivering clinician may use any of these maneuvers; specific details will be determined by the clinical judgment of potential or ongoing efficacy at the time of delivery. We suggest that the more general descriptive term “rotational maneuvers” be used rather than the antiquated use of the name of the original describer of the technique.
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