Shoulder dystocia is a potentially fatal complication that can occur during the
second stage of labor. In this condition, the baby's head is delivered normally, but the shoulder gets impacted (stuck) in the
vagina and cannot be delivered.
It is estimated that the incidence of shoulder dystocia is 1 - 1.5 % of all babies with birth weight of 2,500 grams (5 pounds 8 ounce).
This incidence increases to 4 - 9 % in babies weighing more than 4000 grams ( 9 pounds 14 ounce) (from American Family Physician).
Causes of Shoulder Dystocia
It is very difficult to predict the occurance of shoulder dystocia. But certain causes do predispose to this development:
- Big baby: The baby may be of a larger size due to hereditary causes. Diabetes, a postdated pregnancy that has gone beyond 42 weeks of pregnancy (postmature baby) and certain congenital causes like macrosomia can also cause the baby to be of a bigger than average size. A normal sized baby may also be comparatively big if the maternal pelvis is smaller than normal.
- Maternal pelvis: Abnormalities in the pelvis either due to diseases like rickets or osteomalacia, pelvic injuries due to accidents and congenital anomalies of the hips can lead to shoulder dystocia.
- Problems during labour: A prolonged labour either due to complications in the first stage of labor or the second stage can be a risk factor for development of shoulder dystocia. Delivery of the fetal head by forceps or vacuum aspiration are also indicators that there is a chance for the baby's shoulders to get impacted.
- Postpartum hemorrhage: Postpartum hemorrhage can occur immediately after the deliver of the baby. It can be either a result of injuries to the maternal tissues or due to failure of the uterus to contract properly after the delivery.
- Maternal injuries: Maternal Injuries like severe vaginal lacerations, perineal tear, extension of the episiotomy wound, fracture of the symphysis pubis joint just under the mons pubis, third degree tear of the perineum from the vagina to the rectum or even uterine rupture can occur.
- Brachial Plexus Injury: : Injury to the nerves in the armpit of the baby is a very common complication of shoulder dystocia. It produces a condition known as Erb's palsy. While in most infants, Erb's palsy recovers spontaneously in 1 year, in others it may remain as a lifelong complication.
- Clavicle Fracture: The clavicle is the shoulder bone of the fetus - it connects the upper part of the breastbone to the shoulders and is liable to get fractured during manipulations to release the impacted shoulder.
- Other Complications: Other less common complications like fetal hypoxia, fetal death or fracture of the humerus can also occur.
Management / Treatment of Shoulder Dystocia
Shoulder dystocia is an acute emergency that needs to be dealt with on an urgent basis. Since it is difficult to predict which women will develop shoulder dystocia, it is always wiser to be prepared for this emergency in every woman who is in labor.
The steps for management of shoulder dystocia are:
- Episiotomy: The episiotomy should be immediately increased in size and depth to create more space in the vaginal canal.
- Flexion of legs: With the woman lying on her back, the legs are flexed on her thighs, bringing her knees as close to her chest as possible - this widens out the vaginal opening.
- Traction of fetal head: Firm downward traction is made on the fetal head to move the upper shoulder which is impacted under the symphysis pubis. It is important to note that too much pressure must not be appplied on the head as there could be injury to the neck and nerves causing brachial plexus injury.
- Suprapubic Pressure: Pressure is applied just above the symphisis pubis. The direction of pressure must be downwards and forwards. This helps to move the upper shoulder and causes it to slide under the bone.
- Internal Rotation: If the baby is not born by the above maneouvers, the doctor should insert her hand into the vagina and attempt to maneouver the upper shoulder - she should press on it so that the shoulders get more flexed and the breadth of the shoulders reduced. This can disimpact the shoulders, helping the baby to be delivered.
- Delivering the posterior arm: The doctor needs to insert her hand into the vagina, take hold of the posterior arm and sweep it across the fetal chest , keeping the elbow flexed to prevent injury to the humerus (upper arm bone). The arm is then pulled out of the vagina gently - this decreases the diameter of the fetal shoulders , disimpacting the upper shoulder.
- Changing the position of the patient: The patient is made to get up in a all-fours position, so that the baby falls forward and the shoulder gets disimpacted.
- Other Options: If all maneouvers fail, then the only options left to the doctor are:
- Break the collar bone or clavicle to decrease the diameter of the shoulders.
- Use a hook under the baby's armpit to deliver it.
These are both potentially fatal maneouvers causing injury as also death to the fetus.
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