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Shoulder dystocia means difficulty with delivery of the fetal shoulders.

Although this is more common among women with gestational diabetes and those with very large fetuses, it can occur with babies of any size. Unfortunately, it cannot be predicted or prevented. It probably occurs to some degree in between 1% and 5% of all deliveries, depending on the patient population, the experience of the operator, definitional differences, and the accuracy of reporting.

Shoulder dystocia is a dangerous condition because:

1. If not relieved, it can lead to fetal death, and

2. There is a significant risk of injury to the nerves in the neck from stretching or tearing.

Suspect a shoulder dystocia if, after delivery of the head, the fetal head partially withdraws back into the birth canal (the "Turtle Sign"). This occurs because the anterior shoulder is stuck behind the pubic symphysis. Insert one finger vaginally, and you will be able to feel the shoulder stuck behind the pubic bone.

In more severe cases, the posterior shoulder may be stuck at the level of the sacral promontory.

You should immediately call for extra help since many of the maneuvers you will need to perform will require more than a single person.

Avoid Excessive Downward Traction
Try to avoid applying excessive downward traction to the baby's head. This traction can cause or aggravate injury to the nerves in the neck and shoulder (brachial plexus palsy).

While most of these nerve injuries heal spontaneously and completely, some do not.

Generous Episiotomy
A generous episiotomy can be helpful. If a spontaneous laceration has occurred, or if the perineum is very stretchy and offers no obstruction, then it is not necessary to also perform an episiotomy. However, if there is any soft tissue obstruction or if the perineum interferes with your ability to perform extraction maneuvers, it is wise to place a large episiotomy, a second episiotomy, or extend a perineal laceration with scissors to obtain more room. Some physicians will perform an intentional 4th degree extension (proctoepisiorrhaphy) in order to facilitate delivery. The 4th degree extension can usually be easily repaired without any long-term consequences for the mother and provides excellent exposure for the delivery.

Gentle downward traction can be attempted initially to try to free the shoulder.

If this has no effect, do not exert increasing pressure. Instead, try some alternative maneuvers to free the shoulder.

MacRobert's Maneuver
The MacRobert's Maneuver involves flexing the maternal thighs tightly against her abdomen. This can be done by the woman herself or by assistants.

By performing this maneuver,

1. The axis of the birth canal is straightened, allowing a little more room for the shoulders to slip through, and

2. The pressure of the mother's thighs on her abdomen provides the equivalent of suprapubic pressure to dislodge the shoulder from behind the pubic bone.

With the patient in the MacRobert's position, you can try gentle downward traction again. If gentle traction has no effect, stop the traction and try another maneuver.

Suprapubic Pressure
Suprapubic pressure can be applied to drive the fetal shoulder downward, clearing the pubic bone.

It is usually easiest to have an assistant apply this downward pressure while you apply coordinated, gentle downward traction and the mother bears down.

Sometimes, the suprapubic pressure is more effective if applied in a somewhat lateral direction, rather than straight down. This tends to nudge the shoulder into a more oblique orientation, which in general provides more room for the shoulder.In other cases, straight downward pressure is just what is need to disimpact the fetal shoulder.

Gentle downward traction on the fetal head in combination with this suprapubic pressure, maternal pushing efforts and MacRobert's position may relieve the obstruction. If not, stop the pushing and pulling efforts, and try another maneuver.

Deliver the Posterior Arm
Often, by the time the fetal head has delivered, the posterior arm has entered the hollow of the sacrum. By reaching in posteriorly and sweeping the arm up and out of the birth canal, enough additional space will be freed to allow the anterior shoulder to clear the pubic bone.

This graphic makes the maneuver look easier than it is. Because of limited visibility and space, this maneuver is sometimes difficult or impossible.

Identify the posterior shoulder and follow the fetal humerus down to the elbow. Then you can identify the fetal forearm. Grasping the fetal wrist, draw the arm gently across the chest and then out. Once the posterior arm has delivered, you can try each of the previous maneuvers again as you have reduced the bisacromial diameter and it will be easier for the anterior shoulder to descend.

Screw Maneuver
If you try to remove an electric light bulb by simply pulling on it, it won't work. If, however, you unscrew the light bulb, it comes out relatively easily.

The concept of unscrewing the light bulb can be applied to shoulder dystocia problems.

This example shows pushing the anterior shoulder in a counterclockwise direction. As the baby rotates, the posterior shoulder comes up outside of the subpubic arch. At the same time, the stuck anterior shoulder is brought posteriorly into the hollow of the sacrum. As the rotation continues a full 360 degrees, both shoulders are rotated (unscrewed) out of the birth canal.

It is sometimes easier to perform this maneuver with your hand on the posterior shoulder, rotating it up. If you have enough room in the pelvis, using both your hands, one on the posterior shoulder and one on the anterior shoulder can produce excellent results.

In cases where both the anterior and posterior shoulder are stuck, the baby may need to be rotated twice. The first rotation brings a shoulder down into the hollow of the sacrum, while the second rotation brings that shoulder up and outside the subpubic arch.

Two variations on the unscrewing maneuver include:

• Shoving the shoulder towards the fetal chest ("shoving scapulas saves shoulders"), which compresses the shoulder-to-shoulder diameter, and

• Shoving the anterior shoulder rather than the posterior shoulder. The anterior shoulder may be easier to reach and simply moving it to an oblique position rather than the straight up and down position may be sufficient

Applying fundal pressure in coordination with other maneuvers may, at times, be helpful. Applied alone, it may aggravate the problem and increase the risk of injury by further impacting the shoulder against the symphysis. You also run the risk of uterine rupture if the fundal pressure is applied too vigorously or at the wrong time.

If these maneuvers have failed, it is appropriate to repeat them in various combinations, and with increasing forcefulness. While the increased forcefulness may increase the risk of shoulder injury, the baby must ultimately be delivered or it will die.

Despite careful attention to detail and skillful performance of these maneuvers, some babies will still have a nerve injury. No maneuver, no matter how skillfully performed, can prevent all nerve injuries. But the best chance for avoiding injuries comes when shoulder dystocia is approached in a careful, systematic way, with progressive increases in the forcefulness of the maneuvers, until just the right combination of just the right forces delivers the baby.

OB-GYN 101: Introductory Obstetrics & Gynecology
© 2003, 2004, 2006 Medical Education Division, Brookside Associates, Ltd.
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