Erb’s palsy is a type of brachial plexus injury (nerve injury) that can occur in babies during childbirth and which affects movement and feeling in the arm. Depending on the causes of Erb’s Palsy and the severity of the injury, it could be a temporary or permanent condition.

Here you can discover more about the brachial plexus nerves and the risk of injury when shoulder dystocia occurs during childbirth. This is when a baby’s shoulder gets stuck against the mother’s pelvis after the head is delivered, and additional help is required to release it.

Understanding brachial plexus injury

What factors are associated with brachial plexus injury during childbirth?

How does shoulder dystocia occur?

The importance of the baby’s position in shoulder dystocia

What signs indicate shoulder dystocia?

How should shoulder dystocia be managed?

What can go wrong with shoulder dystocia?

Understanding brachial plexus injury

The brachial plexus is a network of nerves that emerge from the spinal cord through the vertebrae (neck bone) before passing under the collarbone to distribute down the arm. They become the major nerves controlling movement and feeling in the shoulder, elbow, wrist and hand.

They emerge from the vertebrae as four cervical nerve roots, referred to as C5, C6, C7 and C8 and the first thoracic nerve root (T1). These roots then combine to form three trunks:

  • Nerves C5 and C6 form the upper trunk
  • C7 forms the middle trunk
  • C8 and T1 form the lower trunk.

Brachial plexus damage

As the trunks pass under the collarbone they split into anterior and posterior divisions and then into lateral, posterior and medial cords. The nerves that extend to the arm arise from these cords, including the musculocutaneous, axillary, radial, median and ulner nerves.

These nerves are made up of thousands of fibres responsible for carrying electrical messages between the brain and the muscles. If these nerve fibres are damaged, the flow of messages from the brain are weakened or disrupted, and this can stop the corresponding muscles from working properly, if at all.

Type and extent of nerve damage

The symptoms and severity of Erb’s palsy can vary depending on which nerve(s) in the brachial plexus are damaged and whether they are stretched, torn (ruptured) or severed from the spinal cord (avulsed).

Damage to the baby’s upper trunk (nerve roots C5 and C6) is most common in brachial plexus injuries during childbirth. If the nerves are stretched or bruised (i.e. the injury is mild), they may heal themselves without treatment within a matter of months. This is the case in 90% of mild brachial plexus injuries to the upper trunk.

If all of the nerves in the group (C5 to T1) are damaged, then an entire shoulder, arm and hand may be paralysed. If this occurs, the child may also have associated Horner’s syndrome, characterised by a drooping eyelid and constriction of the child’s pupil. Surgery is required to repair the nerves, but few children will fully recover the use of their arm.

For more information on the type and extent of nerve damage to the brachial plexus, please read Grades of Erb’s palsy.

What factors are associated with brachial plexus injury during childbirth?

The nerves in the brachial plexus can be injured when a baby’s head, neck or shoulder is pulled or stretched during a difficult birth. Factors related to Erb’s palsy include:

  • Shoulder dystocia (when the baby’s shoulder is stuck against the mother’s pelvis after the head has been delivered during a vaginal delivery)
  • A difficult or prolonged labour
  • Delivering a very large baby (in excess of 5 kg)
  • Maternal diabetes
  • A shoulder dystocia in a previous pregnancy
  • Assisted vaginal delivery.

Incidences of brachial plexus injury occur most commonly in vaginal births with normal presentation. Very few incidences occur during breech or caesarean deliveries.

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How does shoulder dystocia occur?

The Royal College of Obstetricians and Gynaecologists classify shoulder dystocia as: “a vaginal cephalic delivery that requires additional obstetric manoeuvres to deliver the fetus after the head has delivered and gentle traction has failed.”

Put simply, it’s the result of one or both of the baby’s shoulders getting stuck (impacted) against the mother’s pelvis after the head has been delivered.

Thankfully the incidence of shoulder dystocia occurring is relatively rare, but there are particular risk factors that may increase its chance, such as:

  • A shoulder dystocia in a previous pregnancy
  • A baby with an anticipated birth weight in excess of 5 kg
  • Diabetic mothers with an anticipated baby weighing in excess of 4.5 kg.

A baby’s shoulder can become impacted when the mother’s pelvic opening is too small to allow for the baby’s shoulders to pass into the birth canal after the head has been delivered. This most commonly occurs with very large babies.

When shoulder dystocia happens, it’s a medical emergency for both mother and baby. Once the fetal head is delivered, the baby’s umbilical cord is likely to be compressed and delivery needs to happen quickly to avoid the baby suffering oxygen deprivation with the risk of brain damage and, at worst, death. For the mother, the risk of a post partum haemorrhage (excessive blood loss) is increased with an obstructed birth.

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The importance of the baby’s position in shoulder dystocia

The shoulders can be stuck in either an anterior or posterior position. If the fetal shoulder is impacted in the upper pelvis against the mother’s pubic bone, it’s described as ‘anterior’. If the shoulder is impacted against the lower pelvis – the mother’s sacral promontory – it’s described as ‘posterior’.

If your child has suffered a brachial plexus injury during childbirth and you’re considering making a claim for medical negligence, it’s important to determine whether the affected shoulder was anterior or posterior at the time of delivery. It is only in cases where we can establish that the affected shoulder was anterior that we will succeed. Injuries to the brachial plexus resulting from shoulders being stuck in a posterior position are rarely as a result of negligent handling by the midwife or obstetrician. See Erb’s palsy legal issues.

anterior and posterior positions

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What signs indicate shoulder dystocia?

Once the baby’s head is delivered, the obstetrician or midwife should apply very gentle lateral traction (pull) on the head to test for the progress of the rest of the body with the next contraction. A delivery is described as ‘obstructed’ when:

  • There had been a slow and difficult delivery of the baby’s head
  • There is no movement of the body towards delivery
  • The baby’s head retracts back into the uterus and the neck appears to be rolled, called ‘turtle necking’
  • After the baby’s head has been delivered, the head does not rotate back to restore its normal relationship with the shoulders to aid delivery (a process called restitution).

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How should shoulder dystocia be managed?

Once shoulder dystocia is diagnosed, midwives and obstetricians should follow set emergency procedures to release the shoulders. These include:

1. Immediately calling for additional help by pressing the emergency buzzer.

2. Placing the mother in the ‘McRoberts’ position. This is when she is placed on her back and her legs are removed from stirrups. Two people are required to flex each of the mother’s leg backwards at the same time towards the mother’s head to widen the pelvis.

3. If Step 2 is not effective, while still in the McRobert’s position, a third person should apply suprapubic pressure by pressing down just above the maternal pubic bone in an effort to encourage the fetal shoulder to descend down into the pelvis and under the bone. Gentle traction should be applied to deliver the baby.

4. If Step 3 is not effective, the mother could be placed in the ‘all fours’ position to help widen the pelvis.

5. If Step 4 fails, an episiotomy (cutting the vagina) will allow additional room for the obstetrician to place all of his hand into the vagina to either rotate the baby or to deliver its posterior arm. Both of these internal manoeuvres allow for the upper shoulder to be released and for the body to be delivered.

6. It is rare that the above manoeuvres fail to deliver the baby. Otherwise, the options are limited to:

  • Breaking or bending the fetal clavicle to reduce the width of the baby
  • Undertaking a symphysiotomy – a surgical procedure in which the cartilage of the pubic symphysis is divided to widen the pelvis
  • Undertaking the Zavanelli manoeuvre where the fetus is pushed back up into the uterus to prepare for an emergency caesarean section.

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What can go wrong with shoulder dystocia?

Medical negligence claims for Erb’s palsy usually arise for two reasons:

  • The mother should have been advised to undergo a caesarean section due to the risks of shoulder dystocia
  • The team delivering the baby failed to properly execute the emergency procedures and instead applied excessive traction to the fetal head in an attempt to deliver the baby.

When shoulders are stuck, excessive pull on the baby’s head is known to cause damage to the brachial plexus nerves. The extent of damage is usually in relation to the force and angle of the pull. See also Grades of Erb’s palsy .

Absence of adequate shoulder dystocia training

Growing evidence suggests that those who’ve had insufficient training on the management of shoulder dystocia are more likely to use excessive force when applying traction to the fetal head, carrying with it the risk of brachial plexus injury.

Poorly executed internal manoeuvres during delivery

Internal manoeuvres are very difficult to perform, especially if there has been inadequate training or the obstetrician is inexperienced.

Common internal manoeuvres that help to rotate the baby’s position and release the shoulders are the Woods’ screw manoeuvre and Rubins II. These manoeuvres require the midwife or obstetrician to insert their hands into the vagina to manipulate the baby’s position. They may also attempt to deliver the posterior arm first (to allow more space for the upper body to be delivered), but a frequent mistake is attempting to deliver the shoulder first, instead of the arm.

Good record keeping allows for a review of the birth if necessary and for lessons to be learnt. The Royal College of Obstetricians and Gynaecologists (RCOG) has produced a pro-forma that should be completed in the event of shoulder dystocia. It clearly sets out all of the information required in the medical records to give an accurate account of the birth, including who was involved and exactly what procedures were taken to relieve the obstruction.

If a medical negligence claim is brought, these records become very important. See Erb’s palsy legal issues.

See also Grades of Erb’s palsy
See also Symptoms of Erb’s palsy

Further reading on shoulder dystocia:
Green-top Guideline No. 42 2nd edition, Shoulder Dystocia, Royal College of Obstetricians and Gynaecologists

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