Following shoulder dystocia deliveries, 20% of babies will suffer some sort of injury, either temporary or permanent. The most common of these injuries are damage to the brachial plexus nerves, fractured clavicles, fractured humeri, contusions and lacerations, and birth asphyxia.

The brachial plexus consists of the nerve roots of spinal cord segments C5, C6, C7, C8, and T1. (See accompanying diagram). These nerve roots form three trunks which divide into anterior and posterior divisions. The upper trunk is made up of nerves from C5 and C6, the middle trunk from undivided fibers of C7, and the lowermost trunk is made up of nerves from C8 and T1.

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There are two major types of brachial plexus injury: Erb palsy and Klumpke palsy.

Erb palsy, the more commonly occurring of the two forms of brachial plexus injury, involves the upper trunk of the brachial plexus (nerve roots C5 through C7). This palsy affects the muscles of the upper arm and causes abnormal positioning of the scapula called "winging". The supinator and extensor muscles of the wrist that are controlled by C6 may also be affected. Sensory deficits are usually limited to the distribution of the musculo-cutaneous nerve. Together, these injuries result in a child having a humerus that is pulled in towards the body (adducted) and internally rotated. The forearm extended. Some have described this as the "waiters tip" position.

Klumpke palsy involves lower trunk lesions from nerve roots C7, C8, and T1. In this injury the elbow becomes flexed and the forearm supinated (opened up, palm-upwards) with a characteristic clawlike deformity of the hand. Sensation in the palm of the hand is diminished.

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It has been traditionally thought that most brachial plexus injuries result from stretching of the nerves of the brachial plexus during delivery. While this likely accounts for many brachial plexus injuries, reports of such injuries following deliveries in which there was no shoulder dystocia has led investigators to question whether or not brachial plexus injuries might have other etiologies. Such etiologies might be intrauterine cerebrovascular accidents (strokes), overstretching of the brachial plexus from fetal movement during the pregnancy, or basic maldevelopment of the brachial plexus.

In some brachial plexus injuries sympathetic nerve fibers that traverse T1 can be damaged. This can result in depression of the eyelid and drooping of the mouth on the affected side, a constellation of symptoms called Horner's Syndrome.

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Incidence of brachial plexus injury

Brachial plexus injury is the classic injury following shoulder dystocia. First described by Duchenne in 1872, it occurs following roughly 10% of all shoulder dystocia deliveries as reported in a variety of studies:

Gherman (1998) 16.8%

McFarland (1996) 8.5%

Bofill (1997) 9.5%

Baskett (1995) 13%

Stallings (2001) 12.7%

Nocon (1993) 15.1%

The incidence of shoulder dystocia rises with many factors, the most prominent of which are the size of the baby and maternal diabetes status. Given that roughly one half of 1% of all babies experience shoulder dystocia during delivery and that approximately 10% of shoulder dystocia deliveries result in brachial plexus injuries, the theoretical rate of brachial plexus injury following shoulder dystocia is roughly one in 2000 deliveries. This prediction is confirmed by observation.

Brachial plexus injuries can also occur without there having been a shoulder dystocia. There are multiple reports in the literature of brachial plexus injuries following vaginal deliveries without shoulder dystocia, subsequent to breech deliveries, and even after otherwise uncomplicated cesarean sections. In fact, the rate of brachial plexus injury in which no shoulder dystocia was reported has been quoted to be as high as 40% to 50%. These findings are discussed in detail on subsequent pages on this site.

The natural history of brachial plexus injury

Fortunately, most brachial plexus birth injuries are transient. The majority of such injuries resolve by three months, with a range of two weeks to 12 months. Only 4 to 15% result in some degree of permanent injury:

Rate of brachial plexus injuries that persist permanently

Eckert (1997) 5-22%

Johnson (1979) 7.8%

Graham (1997) 20%

Sandmire (1988) 11.8%

Nocon (1995) 4%

Average: ~10%

Patients with upper lesions -- Erb palsy -- have a better prognosis than those with lower brachial plexus injuries-Klumpke palsy. Whereas upwards of 90 to 95% of all Erb palsies totally resolve, only 60% of Klumpke palsies do. Interestingly, those brachial plexus injuries associated with non-shoulder dystocia deliveries persist more often than those occurring following deliveries in which a shoulder dystocia was documented.

Brachial plexus injuries can also produce secondary effects. Muscle imbalances produced in the hand, arm, and shoulder may result in osseous deformities of the shoulder and elbow and in dislocations of the radial head. The development of the affected arm may be compromised, resulting in its being as much as 10 cm shorter than the nonaffected arm.

Treatment options and prognosis

As mentioned, the majority of brachial plexus injuries will resolve spontaneously over the course of several months to a year. Physical therapy is usually employed within weeks of birth to help strengthen muscles whose nerve supply has been damaged. For those injuries that are permanent there are two modes of therapy.

First, physical therapy can strengthen muscles that are only partially denervated, strengthen surrounding muscles to compensate for functional loss, and improve the range of motion of the affected shoulder, arm, elbow, or hand.

Second, surgical therapy in the form of nerve grafting or muscle transposition may be undertaken. There is, however, great controversy about the efficacy of such surgical procedures in improving the outcome of those with brachial plexus injuries. Several orthopedic and neurosurgeons from around the country who do this sort of surgery frequently report various degrees of improvement in many of their patients. Others in the field, however, refute these claims and feel that there is little or no benefit to such surgery.

Fractured clavicle

The second most common injury suffered by infants following shoulder dystocia deliveries is a fractured clavicle. The incidence of this injury following shoulder dystocia is 10%.

If the fetal shoulders and chest are relatively large in relation to the maternal pelvis, significant pressure may be placed on them as they pass through the birth canal following delivery of the fetal head. In some infants, this pressure causes the clavicle to fracture. The overlapping of the ends of the broken clavicle reduces the diameter of the fetal chest and intra-shoulder distance and allows them to be delivered. This "safety valve" effect may in fact help reduce the incidence of severe brachial plexus injury.

The baseline clavicular fracture rate for all deliveries appears to be about 0.3%. Despite the fact that shoulder dystocia increases the risk of clavicular fracture 30 fold, approximately 75% of clavicular fractures are not associated with shoulder dystocia. Interestingly, although there are multiple reports of brachial plexus injuries following cesarean sections, clavicular fractures following cesarean sections are extremely rare.

Fractured humerus

This occurs in approximately 4% of infants with shoulder dystocia deliveries. Such injuries heal rapidly and are rarely result in litigation.

Contusions

The force with which the infant's shoulder is compressed against the maternal pubic bone and the pressure of the deliverer's hands on the fetus while performing various maneuvers to effect delivery will often result in bruises on the baby's body. Such bruising has often been cited by plaintiff attorneys as evidence that a baby has been handled roughly at delivery despite the fact that such bruises are common even in routine deliveries not involving shoulder dystocia or fetal injury.

The most feared complication of shoulder dystocia is fetal asphyxia. It has been frequently demonstrated in both animal experiments and in retrospective analyses of babies born following dramatic cessation of umbilical blood flow (placental abruption, uterine rupture, etc.) that if babies are not delivered within five to 10 minutes they will suffer irreversible neurologic damage or death. Wood, in an often-quoted article from 1973, showed that in the time between delivery of the head and trunk of an infant, the umbilical artery pH declines at a rate of 0.04 units per minute. This means that at the five-minute mark following delivery of the fetal head, the baby's pH may have dropped from 7.2 -- a common level after several hours of pushing -- to 7.0, the level that defines asphyxia. By 10 minutes the pH would have dropped to 6.8. Ouzounian (1998) reported that of 39 babies whose deliveries involved shoulder dystocia, 15 who suffered brain injury averaged a head-to-shoulder delivery interval of 10.6 minutes while the 24 babies also born following shoulder dystocia but without brain injury had a head-to-shoulder delivery interval of only 4.3 minutes. Cerebral palsy and fetal death are rare but unfortunately not unheard of consequences of prolonged head-to-shoulder delivery intervals following shoulder dystocia deliveries.

The reason for the increasing acidosis and asphyxia that occurs during a shoulder dystocia delivery is that once the fetal head emerges from the mother, the baby's umbilical cord becomes tightly compressed between its body and that of the mother's birth canal. This significantly decreases or totally cuts off blood flow between the mother and infant. If the pressure on the cord is not rapidly relieved, the consequences of cessation of lack of umbilical flow -- decreased delivery of oxygen to the fetus -- will occur.

Maternal injuries

The mother, too, is at some risk when shoulder dystocia occurs. The most common complications she may suffer are excessive blood loss and vaginal and vulvar lacerations.

Significant blood loss, which occurs in one quarter of all shoulder dystocia deliveries, may be seen either during the delivery or in the postpartum period. Its usual causes are uterine atony or lacerations of the maternal birth canal and surrounding structures. Such lacerations may involve the vaginal wall, cervix, extensions of episiotomies, or tears into the rectum. Uterine rupture has also been reported.

Because of the pressure directed upwards towards the bladder by the anterior shoulder in shoulder dystocia deliveries, post-partum bladder atony is frequently seen. Fortunately, it is almost always temporary. Occasionally the mother's symphyseal joint may become separated or the lateral femoral cutaneous nerve damaged, most likely the result of overaggressive hyperflexion of the maternal legs during attempts at resolving the shoulder dystocia.

Ramifications

Even though shoulder dystocia occurs in only 0.5% to 1.0% of all deliveries, the fact that there are approximately 4 million deliveries a year in United States means that many thousands of mothers and babies will experience this obstetrical complication. A little math tells the story:

--If the rate of occurrence of shoulder dystocia is approximately 0.5%, and

--If the rate of brachial plexus injury is 10% in these deliveries, and

--If the rate of permanent injury is 10% of all brachial plexus injuries,

then the rate of permanent brachial plexus injury will be one in 10,000 to one in 20,000 deliveries.

This means that there will be approximately 200 to 400 babies born each year in the United States with permanent brachial plexus injuries following shoulder dystocia deliveries. In addition, there will be babies who will suffer severe central neurologic injury such as cerebral palsy from asphyxia. There will even be babies who will die following severe shoulder dystocias. It is for these reasons that shoulder dystocia injuries have become an important area of medical -- and medical-legal -- concern.

The medical concern involves trying to find ways of preventing shoulder dystocia related injuries. The best way to do this, of course, would be to prevent shoulder dystocia from occurring. If this is not possible, then it is necessary to try to find ways to resolve shoulder dystocias with minimal fetal injury when they do occur. However, since many brachial plexus injuries are seen following deliveries where there was no shoulder dystocia, even perfect prediction and prevention of shoulder dystocias would not entirely eliminate the occurrence of brachial plexus birth injuries.

The medical-legal implications of the above are obvious: Given a severely injured infant, if it can be shown that a physician was negligent either in allowing a shoulder dystocia to occur or in his or her handling of the shoulder dystocia once it did occur, then according to our legal system, that physician will be held liable for damages to the injured baby and his or her family.

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