What Causes Erb's Palsy?

Doctor Checking Baby's ArmErb's Palsy is a paralysis of the arm caused by damage to the brachial plexus, the group of nerves near the shoulder. Brachial nerve injuries typically occur during a difficult delivery, but can also happen in the first few months after birth if your child experiences some kind of trauma to the nerve cluster early in its life. If your child is suffering from the effects of Erb's Palsy due to an injury which took place during delivery, you probably have a lot of questions. We understand what you are going through and hope to answer some of your most pressing concerns.

What Causes Erb's Palsy?

The underlying cause of Erb's Palsy is an injury to the upper group of the main nerve cluster of the arms, also known as the brachial plexus. During the delivery process, medical negligence or malpractice can result in damage to your infant's nerves if proper care is not taken. Furthermore, warning signs may be apparent in the weeks leading up to birth that would alert your physician to take extra precaution. For the remainder of this article, the various causes of brachial plexus injuries which can give rise to Erb's Palsy will be listed, so that you have a thorough accounting of the possible causes and are better equipped to know whether proper care was provided during the delivery process.

  • Birth Assistance Tools: As with many other birth injuries, one of the possible causes of Erb's Palsy is the improper use of birth assisting tools. The primary birth assistance tools used by OB/GYNs are obstetrical forceps or vacuum extractors). If used unnecessarily or incorrectly, these tools can place undue stress or pressure on the arm and shoulder area of your infant and injure their brachial plexus, which can result in the development of Erb's Palsy.
  • Fetal Macrosomia: Fetal macrosomia is a condition in which a baby is abnormally large (over 9 lbs.). If your physician fails to adequately monitor fetal size and diagnose macrosomia complications including Erb's Palsy can arise. Fetal macrosomia almost always calls for a scheduled C-section because the risks of vaginal delivery are too high. Larger infants, especially for smaller mothers, often encounter more difficult vaginal deliveries. If the baby's head and shoulder get pushed in opposite directions during birth, these difficulties could result in injuries to the brachial plexus and then Erb's Palsy. As large fetal size should be detectable within the last few weeks of pregnancy, it is absolutely your physician's responsibility to be aware of the potential for related complications and take all necessary precautions. This is especially true with modern medical advancements such as an increased capacity for prenatal monitoring.
  • Abnormal Fetal Presentation: Erb's Palsy is sometimes caused when vaginal delivery is complicated by an abnormal fetal position - such as breech or feet-first. These positions create higher risks of injury and extra care and precaution are required. A feet first pull will usually cause the baby's arms to go over their head, putting too much pressure on the arms and inducing unnatural stress on the brachial plexus. Doctors should be able to identify an abnormal fetal presentation in advance and take necessary precautions which may include ordering a C-section to avoid complications.
  • Excessive Pulling / Force: If your doctor pulls too hard on your baby's arms - during or even after delivery - Erb's Palsy can arise as a consequence. Other types of pulling can result in Erb's Palsy as well - such as if your infant's head and neck are pulled toward the side as their shoulders pass through the birth canal, or if your baby is pulled at an awkward angle with their head turned one direction and their arm in another direction.
  • Shoulder Dystocia: Shoulder dystocia is a common obstetric complication that triples the risk of Erb's Palsy. Shoulder dystocia occurs when the baby's head is delivered, but its shoulders get stuck in the birth canal. Usually, only one shoulder gets stuck and macrosomic (large) babies are at high risk for this. Whatever its particular characteristics may be, shoulder dystocia is considered an emergency and requires a physician well-versed in abnormal births. If the doctor takes too long, shoulder dystocia can be fatal due to umbilical compression. However, if delivery is rushed or performed without adequate care, extensive damage to the nerves can occur resulting in conditions such as Erb's Palsy.

It should also be noted that while Erb's Palsy is most likely to occur during childbirth, it can also result from any kind of major trauma such as physical blows or pressure to the neck during your child's first few months of life. In rare cases, this condition can occur in adults due to damage from injuries or accidents.

What Are the Risks Factors for Erb's Palsy?

As outlined above, the nerve damage that results in Erb's Palsy can be the result of a number of different complications or events during labor and delivery. Sometimes these events are impossible to predict, but there are definitely certain conditions that are known to increase the risk of a complicated vaginal delivery. It is crucial that your physician takes adequate preventive measures to avoid a difficult delivery and acts on any risk factors which may present themselves. Known risk factors associated with Erb's Palsy include:

  • The second stage of labor lasting over an hour
  • A pregnancy lasting over 40 weeks
  • Excessive maternal weight gain
  • A contracted or flat pelvis
  • Maternal diabetes
  • A previous delivery with a brachial plexus injury
Additional Resources on Causes of Erb's Palsy
  1. Gurewitsch ED, Allen RH. Fetal manipulation for the management of shoulder dystocia. Fetal Matern Med Rev 2006; 17-239-80. (What doctors can do to limit the risk of Erb's palsy/shoulder dystocia.)
  2. Jennett RJ, et. al: Erb's palsy contrasted with Klumpke's and total palsy: Different mechanisms are involved. Am J Obstet Gynecol 2002; 186:1216-1220. (Natural forces argument. This article is frequently relied upon by doctors in litigation.)
  3. Sandmire HF, DeMott RK: Erb's palsy causation: a historical perspective. Birth 2002; 29:52-54. (Echoes much of the Jennett article above.)
  4. Allen RH, et. al: Comparing clinician-applied loads for routine, difficult and shoulder dystocia deliveries. Am J Obstet Gynecol 1994;171:1621-7.
  5. Acker DB et al. Risk Factors for Shoulder Dystocia. Obstet gynecol 66;762, 1985. CC-section recommended for diabetic gravidas if fetal weight is thought to be over 4000g.)
  6. Acker DB et al. Risk Factors for Erb's-Duchenne Palsy. Obstet gynecol 71:389, 1988. (The traumatic neuropathies caused by mechanical disruption of the brachial plexus nerve roots, are serious complications of birth.)