Shoulder dystocia is an issue which complicates many deliveries. Once the head has been delivered, the infant's anterior shoulder will sometimes become stuck behind the mother's pubic bone. The obstetrician then has a window of opportunity to deliver the baby without permanent injury to the brain. If improperly handled by the obstetrician, shoulder dystocia can lead to many serious complications including death, brachial plexus palsies (Erb's palsy), clavicular (collar bone) and humeral (upper arm) fractures.
A brachial plexus nerve injury (with resultant Erb's palsy) is caused by excessive traction (pulling too hard on the baby's arm) when attempting to get the baby "unstuck". The nerve can be stretched or avulsed--depending on the force used. The presence of an Erb's palsy strongly suggests that excessive force was applied during the performance of maneuvers to relieve the shoulder dystocia. Many times, the shoulder dystocia can be caused or worsened by the use of too much pitocin (a medication used by physicians to speed or strengthen contraction activity. And it is well known that application of a vacuum or forceps at a mid station or higher can cause a shoulder dystocia to occur. Although some physicians have suggested that nerve damage takes place before delivery, this has been strongly refuted by the vast majority of scientific literature.
Erb's palsy can have lifelong implications for the child because the child may have little or no use of the affected arm or hand. Severity of the disability depends on the degree and location of the injury. Much therapy and several surgeries will probably be required to maximize use the affected limb. This can have a detrimental effect on the child's ability to play sports and limit choices for vocation. Certainly self esteem can be severely affected.
Risk Factors and incidence of Shoulder Dystocia
Many obstetricians believe that the incidence of shoulder dystocia has increased in recent years due to increased fetal weights. Williams Textbook on Obstetrics, 21rst Edition, 2001, McGraw-Hill Publishing, p. 459 Neonates presenting with a shoulder dystocia tend to have significantly greater shoulder-to-head disproportions compared with equally macrocosmic infants delivered without dystocia. Id. The babies tend to be larger (>4000 grams) and it also appears that maternal obesity also plays a significant role in shoulder dystocia. (BMI > 30) Most of the babies were greater than 4000 grams.
In addition to excessive maternal and gestational weight described above, other risk factors include multiparity, maternal diabetes, and post term pregnancy. There is evidence to suggest that a mid pelvic instrumental delivery (by forceps or vacuum extraction) can significantly increase the risk of Shoulder Dystocia. Prolonged first and second stage labor is associated with increased risk of shoulder dystocia. In addition, strong fundal pressure (pushing at the top of the mother's stomach) may result in further impaction of the anterior shoulder. In one study, that the application of fundal pressure in the absence of other maneuvers resulted in a 77% complication rate and was strongly associated with fetal orthopedic injuries and neurologic damage. Williams at pp. 460 & 462.
The true incidence of dystocia is not accurately known because physicians and institutions fail to report many cases. The incidence is somewhere between .2 percent and 1.4 percent of all vaginal deliveries. Williams at p. 459. In England, the incidence was said to be between .23 and 1.1 percent of all vertex vaginal deliveries. British Journal of OBGYN, December 1998, Vol. 105, pp. 1256-1261, Fatal Shoulder Dystocia: A Review of 56 Cases Reported to the Confidential Enquiry into Stillbirths and Deaths in Infancy.
Management of Shoulder Dystocia
Physicians should be prepared to handle a dystocia, especially where there is a high maternal Body Mass Index (BMI) and suspicions of a macrosomic baby. There are a number of maneuvers which obstetricians must perform in a gentle and stepwise fashion to relieve the stuck shoulder. The maneuvers include suprapubic pressure, McRoberts maneuver, Woods corkscrew maneuver, delivery of the posterior shoulder, deliberate fracture of the clavicle, and the Zavanelli maneuver. But, many physicians will elect to perform a Cesarean section without a trial of labor in order to avoid the risk of causing damage to the baby. Certainly there is a dramatic increase in the incidence of Shoulder Dystocia when the baby is more than 4500 grams and a short maternal height are also considered by many physicians to increase the risk of shoulder dystocia--warning signs which the physician should heed of an impending dystocia.
The cause of a Brachial Plexus Injury suggests that there has been a failure to comply with the standard of care and that excessive force has been applied.