Shoulder dystocia cannot be reliably predicted; therefore, all deliveries should be considered to have the potential for a shoulder dystocia. If a woman is considered at risk for shoulder dystocia, the woman, her support person, and the birth attendant’s team should prepare for a shoulder dystocia in advance of delivery of the fetal head. Preparing the team for the possibility of flattening the bed, the McRoberts maneuver, suprapubic pressure, and rolling over can increase cooperation in the event of a shoulder dystocia. In addition, a stool placed at the side of the bed corresponding to the fetal back helps to indicate to the team the location to apply oblique suprapubic pressure. Low-fidelity simulation exercises may be used to improve the aspects of teamwork that may be helpful for the management of shoulder dystocia.
As soon as shoulder dystocia is recognized, several measures have to be taken. The attendant must seek help from other health care personnel. If an obstetrician is not present, he or she should be notified to proceed to the delivery room. An anesthesia and neonatal team should also be called. The most responsible birth attendant should be constantly informed of the time that has elapsed since delivery of the head. An effective way of ensuring this is to designate a timekeeper to document the timing of events. In all instances, one should avoid pulling on the head, pushing on the fundus, panicking, and pivoting (severely angulating the fetal head using the coccyx as a fulcrum). It is important to ask the woman to stop pushing until maneuvers to relieve the shoulder dystocia are carried out.
Several obstetric maneuvers can be used to resolve shoulder dystocia, including the McRoberts maneuver, suprapubic pressure, delivery of the anterior shoulder, delivery of the posterior shoulder and arm, the Wood’s screw maneuver, deliberate fracture of the fetal clavicle or humerus, the Zavanelli maneuver, and maternal symphysiotomy.
The McRoberts maneuver should be attempted first. Delivery of the posterior shoulder appears to be associated with the highest rate of delivery compared with the other maneuvers; thus, it should be considered after the McRoberts maneuver and suprapubic pressure. The need for additional maneuvers is associated with higher rates of neonatal injury. Despite historical recommendations to perform an episiotomy at the time of a diagnosed shoulder dystocia to prevent a brachial plexus injury, the literature does not support a benefit to this practice.
McRoberts Maneuver and Suprapubic Pressure
These two maneuvers are often used simultaneously as the first steps to help resolve shoulder dystocia. About 50 to 60 percent of shoulder dystocias resolve using a combination of McRoberts maneuver and suprapubic pressure, thereby eliminating the need for further maneuvers.
The McRoberts maneuver involves flexing the legs sharply upon the maternal abdomen. This causes the symphysis pubis to rotate cephalad and the sacrum to be straightened with flattening of the lumbar lordosis, thus allowing the fetal shoulder to slide out beneath the maternal pubic bone anteriorly.
An assistant can perform suprapubic pressure (not fundal pressure) by applying oblique pressure (downward toward the pubic bone and laterally toward the fetus’s face or sternum) just above the maternal pubic bone with the heel of their clasped hands against the posterior aspect of the shoulder to dislodge it (Mazzanti maneuver). A stool may be useful to facilitate this maneuver, particularly in the case of a shorter assistant. It is necessary to know the position of the occiput so that pressure is applied from the correct side and is most effective. Shoulder dystocia is caused by an infant’s shoulders entering the pelvis in a direct AP axis instead of the physiologic oblique axis; therefore, pushing the baby’s anterior shoulder to one side or the other from above can often change his or her position to the oblique, thus allowing its delivery.
The birth attendant may also attempt to manually dislodge the anterior shoulder from behind the symphysis pubis. One may place a hand deep in the vagina behind the anterior shoulder and attempt to rotate the axis of the shoulders into the oblique diameter of the pelvis (Fig. 18-2). Firm traction is then applied to the fetal head, deflecting it toward the floor.
A and B. Delivery of anterior shoulder.
Posterior Arm and Shoulder Delivery
If McRoberts maneuver and suprapubic pressure are not successful, the obstetrical care provider should then attempt to deliver the posterior arm. This requires the least amount of force to deliver the baby and results in the lowest amount of stretch on the brachial plexus. The fetal arm is usually flexed at the elbow, and if it is not, pressure in the antecubital fossa can assist with flexion. The hand can then be grasped and swept across the chest and delivered.
The hand of the operator is placed deeply into the vagina along the curvature of the sacrum and behind the posterior shoulder of the fetus. If the back of the fetus is toward the operator’s right side, the left hand is used. If the back is toward the operator’s left, the right hand is preferred (Fig. 18-3A)
The antecubital fossa of the posterior arm is located and using the pressure of a finger, an attempt is made to flex the arm in a fashion similar to the Pinard maneuver in a breech extraction
The forearm is swept across the chest and face, the hand is then grasped, and the arm is extended along the fetal face and delivered (Fig. 18-3B)
Once this has been accomplished, the anterior shoulder delivers in most cases. If it does not, the body is rotated 180° so that the anterior shoulder is now posterior. It is then extracted by the same maneuver. This maneuver tends to increase the risk of fracturing the humerus; however, most humeral fractures heal quickly with no permanent damage. In view of this, it is worth trying this maneuver to resolve the shoulder dystocia of an infant in a life-threatening situation when the other maneuvers have not worked
A and B. Extraction of the posterior shoulder and arm.
Wood’s Screw and Rubin Maneuvers
The Wood’s screw and Rubin maneuvers are rotational maneuvers that can be attempted after a failure of delivery of the posterior arm. In the Rubin maneuver, the birth attendant places their hand vaginally on the back surface of the most easily accessible fetal shoulder (anterior or posterior) and rotates it toward the fetal face. This flexes the shoulders across the chest and decreases the distance between the shoulders, thus decreasing the dimension of the fetal chest that must fit out through the pelvis.
In the Wood’s screw maneuver, the birth attendant pushes the posterior shoulder through a 180° arc by applying pressure on the anterior surface of the posterior shoulder to turn the fetus until the anterior shoulder emerges from under the maternal symphysis. The idea is to progressively rotate the posterior shoulder in a corkscrew fashion to release the opposite impacted anterior shoulder. To perform this maneuver, the posterior shoulder must have passed the spines for this maneuver to be successful. In a situation in which the fetal head position is left occiput transverse (LOT), two fingers of the left hand are placed on the anterior aspect of the posterior shoulder. Pressure is made against the shoulder so that it moves counterclockwise, the posterior aspect leading the way (Fig. 18-4). It is turned 180°, past 12 o’clock. In this way, the posterior shoulder is delivered under the pubic arch. The head has turned from LOT to right occiput transverse (ROT). This should result in delivery of the posterior shoulder, and the anterior shoulder should now be posterior.
Although this maneuver is often described in shoulder dystocia literature, it is rarely performed. The fetal clavicle is a strong bone and not that easy to deliberately fracture. The clavicle may be deliberately fractured by pressing the anterior clavicle against the pubic ramus. The fractured clavicle decreases the bisacromial diameter, facilitating resolution of the dystocia. Serious fetal consequences that may occur include damage to the lungs and major blood vessels.
Rolling Over to “All Fours” Position
Moving the mother onto all fours on her hands and knees (the Gaskin maneuver) may increase the effective pelvic dimensions and allow the fetal position to shift, thereby freeing the impacted shoulder. With gentle downward traction on the posterior shoulder (the shoulder against the maternal sacrum), the anterior shoulder may become more impacted (with gravity) but will facilitate the freeing up of the posterior shoulder.
This maneuver is reserved for catastrophic cases and is associated with a significantly increased risk of fetal morbidity and mortality and maternal morbidity. This is a cephalic replacement maneuver whereby cardinal movements of labor are reversed; the head must first be rotated back to its pre-restitution position, flexed, pushed up, rotated to the transverse, and disengaged, and then a cesarean section is performed. Constant firm pressure is applied from below while the head is pushed back into the vagina. A general anesthetic is often administered in addition to tocolytics to produce uterine relaxation required for this maneuver. Cesarean delivery must be performed immediately after replacement of the head.
This procedure is rarely performed and is usually reserved for areas with no quick access to performing cesarean sections. It involves dividing the ligaments between the right and left pubic symphyseal bones. This results in an increase in the transverse diameter of the pubis by adding about 3 cm to the circumference of the pelvis. The major risk involves potential injury to maternal soft tissues especially the bladder and urethra.