Erb's Palsy Causes
Erb's palsy is caused by stretching or injury to the brachial plexus nerves during childbirth, especially in difficult or complicated deliveries. When the brachial plexus nerves are damaged, it can cause weakness, numbness, or even paralysis of the shoulder, arm, or hand. Learn more about the different causes of Erb's palsy.
What Is Erb's Palsy, and What Causes It?
Erb's palsy (also called Erb-Duchenne palsy) is a type of brachial plexus injury that affects the upper nerve roots (usually C5-C6 and sometimes C7) that control shoulder and upper-arm movement.
When these nerves are stretched, compressed, or torn during birth, the signals from the spinal cord to the shoulder and arm muscles are disrupted. This can lead to symptoms like arm weakness, limited range of motion, or the classic "waiter's tip" position of the arm in newborns.
In most babies, the injury is mild and is highly likely to improve over time. In more severe injuries (such as nerve rupture or avulsion), some weakness or paralysis can be permanent without timely intervention. However, with close monitoring and early therapy, many babies regain most or all function.
What Causes Erb's Palsy During Childbirth?
The most common cause of birth-related Erb's palsy is when the brachial plexus is overstretched. Too much force is applied between the baby's neck and shoulder. This often happens when the baby is stuck in the birth canal and the head or neck is pulled to help free the shoulders.
That stretch can:
- Temporarily injure the nerve (known as neurapraxia)
- Partially tear the nerve (neuroma, rupture)
- Completely pull the nerve root away from the spinal cord (avulsion)
Erb's palsy is more common after difficult vaginal births, but it sometimes occurs (very rarely) during C-sections if the baby's head, neck, or arms are pulled or rotated in a tight space. In fact, only about 1.5% of Erb's palsy cases occur during C-section births.
Erb's palsy is often unavoidable, as medical providers must make decisions quickly to protect the mother and baby. However, there are some cases where brachial plexus injuries leading to Erb's palsy can be considered medical negligence.
Fortunately, most cases of Erb's palsy are mild, and most children will make a full recovery within the first few months to first year of life.
Shoulder Dystocia
Shoulder dystocia happens when after the head is delivered, one of the baby's shoulder becomes lodged behind the mother's pelvic bone and cannot easily pass through the birth canal.
This is the biggest known risk factor and is also the most common cause of Erb's palsy. In fact, childbirths involving shoulder dystocia have nearly a 3 times higher rate of developing Erb's palsy.
While it is impossible to tell if shoulder dystocia will occur during childbirth, there are some maternal and infant risk factors that may increase the likelihood, such as:
- Babies weighing over 8 lbs 13 oz (macrosomia)
- Pregnant with more than one baby, such as twins or triplets (multiple gestation)
- Maternal obesity or diabetes (either before pregnancy or during)
- Maternal age is over 35 years
- Small or unusually shaped maternal pelvis
- Delivery past the due date
- Induction of labor or Pitocin use during high-risk pregnancy
- Previous shoulder dystocia or brachial plexus injury
Excessive Traction on the Baby's Head or Neck
Even without shoulder dystocia, excessive lateral traction (pulling or twisting the baby's head and neck) during delivery can stretch the brachial plexus and cause nerve injury.
This happens most often when:
- The baby is large and difficult to deliver, and extra pulling is used.
- The baby's head is rotated, tilted, or pulled too far while the shoulders are still stuck in the birth canal.
- The baby is pulled by the head rather than using repositioning maneuvers or calling for help.
Quick Fact: Some cases of brachial plexus injuries can also occur purely from the forces of contractions or maternal pushing. This means that not every case of nerve injury is necessarily due to medical negligence or mishandling of delivery.
Improper or Aggressive Use of Delivery Tools
Tools such as forceps and vacuum extractors can save lives when used correctly, but they also carry a risk of nerve injury if they are used with too much force or in the wrong direction.
Erb's palsy may be more likely when:
- Forceps or vacuum are used repeatedly in a difficult vaginal delivery.
- The head is pulled while the shoulders remain stuck behind the pelvis.
- The device is placed incorrectly, requiring extra force to compensate.
Prolonged or Obstructed Labor
When labor is very long, very difficult, or fails to progress, medical providers may attempt multiple interventions to complete a vaginal delivery. Prolonged second stage (pushing) increases the chance of:
- Repeated attempts at traction on the baby's head or shoulders
- Use of forceps or vacuum extractor
- Shoulder dystocia during a tight fit through the pelvis
Which Babies Are at Higher Risk for Erb's Palsy?
Abnormal Fetal Position
Certain fetal positions make it harder for the shoulders and arms to move safely through the birth canal during delivery. This can increase the risk of brachial plexus stretch and make delivery more dangerous.
Most common abnormal positions include:
- Breech presentation (bottom-first or feet-first): The baby's arms may be extended above the head. Pulling on the trunk or arms to speed delivery can stretch the brachial plexus.
- Face, brow, or transverse lie: When the baby is not aligned head-down and centered, delivering the head may require more rotation and traction.
- Occiput posterior: Also referred to as "sunny-side-up," this occurs when the baby's head is down but facing the mother's front.
- Persistent asynclitic positions: The baby's head tips sideways (ear to shoulder) in the pelvis, which can cause slow or dangerous labor if it remains persistent.
Large Babies (Macrosomia)
Fetal macrosomia, meaning babies with birthweights over 8 lbs 13 oz (4000 g), are more likely to experience shoulder dystocia and brachial plexus injuries. Statistics show that medical providers who fail to properly manage babies with macrosomia are nearly 10 times more likely to develop Erb's palsy than those who weigh less.
Other Causes of Erb's Palsy
Although rare, there are some cases of Erb's palsy that are not caused during childbirth, such as:
- Falls
- Contact sport injuries (football)
- Car accidents or motor collisions
- Surgery
- Bullet wounds
- Tumors putting pressure on nerves
What Are the Long-Term Effects of Erb's Palsy?
Depending on the severity of nerve damage, children with Erb's palsy may experience a variety of different symptoms that can affect their strength, mobility, and daily life.
- Weakness in the shoulder or arm
- Limited range of motion
- Paralysis (in severe cases)
- Asymmetrical arm size or length
- Muscle atrophy (loss of muscle mass)
- Shoulder dislocation or subluxation (partial dislocation)
- Abnormal limb growth (arm may appear shorter or thinner)
- Unusual posture (asymmetry can affect balance and stature)
- Pain, fatigue, and aching around the shoulder, neck, upper back, or arms
- Emotional and social impact can affect self-esteem and confidence
Is Erb's Palsy Always Caused by Medical Negligence?
No, not all cases of Erb's palsy are caused by medical negligence. However, a difficult delivery or existing maternal and infant risk factors can cause situations that may increase the risk of negligence-related Erb's palsy, such as:
- Failing to recognize or plan for known risk factors (maternal diabetes, macrosomia, prior shoulder dystocia, etc).
- Excessive lateral traction on the baby's head or neck instead of recommended maneuvers.
- Using forceps or a vacuum aggressively without clear indication, or continued attempts despite signs of a stuck shoulder.
- Delaying a medically necessary C-section in a clearly high-risk situation.
Many cases of Erb's palsy are also due to unavoidable situations. Parents who suspect their child's Erb's palsy may have been caused by medical negligence should consult a pediatric specialist and a birth injury lawyer to determine potential prognosis, treatment, and legal options.
Erb's Palsy Causes FAQs
Written and Medically Reviewed by:
Cerebral Palsy Hub Team
Cerebral Palsy Hub was founded to help support children and their families with cerebral palsy and to create a safe space for those affected. We strive to provide the most accurate, up-to-date information, and tools to help give your child the life they deserve.
Last Updated: December 7, 2025
