Why Is My Baby’s Arm Weak After Delivery? Erb’s Palsy, Fractures, and Nerve Injury Signs

When you notice your newborn’s arm isn’t moving the same way as the other, or seems limp or weak after delivery, it’s natural to feel concerned and want to understand what might be happening. Arm weakness in a newborn can have several causes, some related to the delivery process itself. Recognizing what you’re observing and seeking prompt medical evaluation can help your baby’s care team identify the cause and decide whether monitoring, imaging, therapy, or specialist follow-up is needed.

This article explains what arm weakness looks like in newborns, describes the main causes including nerve injuries and fractures, and guides you on what to document and discuss with your baby’s medical team.

What Arm Weakness in Newborns Looks Like

Arm weakness in a newborn typically means you notice a difference in how one arm moves compared to the other. This difference is usually visible soon after birth, though sometimes it becomes more apparent over the first hours or days.

Observable Movement Differences Between Arms

You might see that one arm moves less during spontaneous activity, like when your baby stretches or reacts to sounds. The affected arm may not lift away from the body as much, or the elbow might not bend and straighten the same way. When you gently move the arm, it might feel floppy or offer less resistance than the other arm.

The hand may still move and grasp even when the shoulder and upper arm show weakness. This pattern can help distinguish between different types of injury.

Common Positions and Postures Parents Notice

A weak arm often rests in a characteristic position. The arm may stay close to the body with the elbow straight or slightly bent, and the hand might turn inward. Some babies hold the affected arm in what clinicians may call a “waiter’s tip” position, where the shoulder rotates inward, the arm rests close to the body, and the forearm or hand turns backward.

You might also notice asymmetry during reflexes. The Moro reflex, which happens when a baby is startled, normally causes both arms to extend outward and then come back together. With arm weakness, one side may not respond the same way as the other.

Three Main Causes of Arm Weakness After Delivery

Birth-related arm weakness may involve a nerve injury, a bone injury, soft tissue discomfort, positioning-related weakness, or a combination of factors. Understanding these categories helps you describe what you’re seeing to your baby’s medical team.

Nerve Injury vs Bone Injury vs Other Causes

Nerve injuries affect the signals that control arm movement. The brachial plexus is a network of nerves near the neck and shoulder that provides movement and feeling to the shoulder, arm, hand, and fingers. When these nerves are stretched or compressed during delivery, movement and strength can be affected. This type of injury is what causes Erb’s palsy and other brachial plexus injuries.

Bone injuries, most commonly clavicle fractures, can also limit arm movement. In these cases, the baby typically avoids moving the arm because it causes pain rather than because the nerves aren’t working properly.

Other less common causes include temporary nerve compression from positioning during delivery or, rarely, other neurological conditions that affect movement.

Erb’s Palsy and Brachial Plexus Injury

Erb’s palsy is one of the most common explanations for arm weakness noticed after delivery. It involves injury to the upper portion of the brachial plexus nerve network.

What the Brachial Plexus Does

The brachial plexus consists of five nerve roots that branch out from the spinal cord in the neck and travel through the shoulder area to the arm. These nerves control all the movements of the shoulder, arm, forearm, hand, and fingers. Different sections of the brachial plexus control different parts of the arm.

The upper nerves primarily control shoulder movement and elbow bending. The middle nerves affect the forearm and wrist. The lower nerves control the hand and fingers.

How Delivery Trauma Can Injure These Nerves

During a difficult delivery, the brachial plexus nerves can be stretched or injured if the baby’s neck and shoulder area are placed under excessive traction or pressure. The injury can range from temporary stretching to more serious nerve damage. This can happen during shoulder dystocia, when one or both of the baby’s shoulders becomes stuck after the head has delivered, although not every brachial plexus injury occurs in the same way.

The injury can range from mild stretching that heals on its own to more severe damage that requires specialized treatment. The extent of injury affects which arm movements are impacted and how recovery progresses.

The “Waiter’s Tip” Position

When Erb’s palsy affects the upper brachial plexus nerves, babies often hold their arm in the waiter’s tip position. The shoulder rotates inward, the elbow stays straight, and the forearm turns so the palm faces backward or outward. The arm hangs limply at the side.

This position occurs because the muscles controlled by the injured nerves can’t work properly, while other muscles in the arm continue to function. A baby with upper brachial plexus involvement may have difficulty moving the shoulder or bending the elbow, while finger movement may be partly or fully preserved.

Clavicle and Arm Fractures During Birth

Fractures of the clavicle (collarbone) are another common birth-related injury that can affect how a baby moves their arm. Clavicle fractures are recognized birth injuries and may be seen after difficult deliveries or deliveries involving larger babies.

How Fractures Present Differently Than Nerve Injuries

A baby with a clavicle fracture typically moves the arm less because movement causes pain, not because the nerves aren’t sending signals properly. You might notice your baby cries when you pick them up under the arms or when you move the affected arm during dressing or bathing.

Unlike nerve injuries where the arm may feel floppy, a fractured clavicle often causes the baby to hold the arm protectively close to the body in a guarded position. The hand and fingers usually move normally, and the baby can grasp, but resists larger arm movements.

Pain and Tenderness as Key Clues

With a fracture, there may be tenderness, swelling, or a bump over the clavicle area. The baby might react with crying or pulling away when that area is touched. Some parents notice a grinding or clicking sensation, though this isn’t always present.

In contrast, nerve injuries may cause weakness or reduced movement without the same clear tenderness over a bone. A medical exam is still needed because parents cannot reliably distinguish nerve injury from fracture based on pain alone.

Other Nerve Injuries That Affect Arm Movement

While Erb’s palsy is the most common pattern, other types of brachial plexus injuries can occur and affect different parts of the arm.

Total Brachial Plexus Injury

A more extensive brachial plexus injury can affect most or all of the arm, causing severe weakness or little movement from the shoulder through the hand. The arm hangs completely limp with no movement at the shoulder, elbow, wrist, or hand. This is less common than Erb’s palsy but represents a more extensive injury.

Babies with a more extensive plexus injury may have very limited movement, reduced reflexes, and weakness affecting the shoulder, elbow, wrist, and hand.

Lower Nerve Involvement

Injuries to the lower portion of the brachial plexus, sometimes called Klumpke’s palsy, primarily affect the hand and wrist while shoulder and elbow function may be preserved. This pattern is rare in newborns and should be evaluated by a medical professional if hand or wrist movement appears weak, absent, or very different from the other side.

Parents might notice the baby can move the shoulder and bend the elbow but has a weak or immobile hand and wrist.

Delivery Factors That Increase Injury Risk

Certain circumstances during delivery are associated with a higher likelihood of birth-related arm injuries. Understanding these factors doesn’t determine whether a specific injury was preventable, but helps explain why some babies experience these complications.

Shoulder Dystocia and Difficult Extraction

Shoulder dystocia and birth injuries are closely connected. When the baby’s shoulder becomes stuck after the head delivers, additional maneuvers are needed to complete the delivery. These maneuvers can place stress on the brachial plexus nerves or the clavicle.

Shoulder dystocia itself is often unpredictable, though certain factors like gestational diabetes, larger estimated baby size, or prolonged labor may increase the likelihood. Even with careful management, shoulder dystocia can result in injury.

Baby Size and Position

Larger babies may have a higher risk of difficult delivery and shoulder dystocia, which can increase concern for birth-related arm injury. The baby’s position during delivery also matters. Babies in certain positions may require more assistance or maneuvering during delivery, which can increase stress on the shoulder and arm area.

Use of forceps or vacuum assistance may appear in the delivery history when a birth was difficult, but the medical team must review the full record to understand whether and how those factors relate to the baby’s arm weakness.

Signs That Require Immediate Medical Attention

While any noticeable arm weakness should be evaluated, certain signs indicate a need for urgent medical assessment.

When Arm Weakness Comes With Other Symptoms

Seek immediate medical care if your baby’s arm weakness occurs alongside difficulty breathing, bluish color around the mouth, extreme lethargy, seizure-like movements, poor feeding, fever, or a sudden change in alertness. These symptoms could indicate a more serious neurological problem beyond a birth-related arm injury.

If your baby shows signs of significant pain, such as persistent crying that isn’t soothed by feeding or holding, or if the baby screams when touched in certain areas, prompt evaluation is important to identify and address the cause.

Complete Immobility or Severe Pain

An arm that shows absolutely no movement at all, even in the fingers, or that causes severe distress with any touch or position change, warrants immediate assessment. While many birth-related arm injuries improve with time, complete paralysis or extreme pain may require urgent intervention.

If you notice new symptoms developing after the first day or two, such as increasing weakness, swelling, or changes in skin color or temperature of the arm, contact your pediatrician promptly.

What to Document When You Notice Arm Weakness

Careful observation and documentation help your baby’s medical team understand what’s happening and track changes over time.

Movement Observations to Record

Note which arm is affected and which specific movements you don’t see. Can your baby move the fingers? Does the wrist bend? Can the elbow flex? Does the shoulder lift away from the body? Write down what you observe during different activities like feeding, bathing, or when your baby is awake and active.

Pay attention to whether the affected arm participates in reflexes like the Moro reflex or grasp reflex. Note if your baby startles symmetrically with both arms or if one side responds differently.

Timing and Circumstances

Record when you first noticed the weakness. Was it immediately after birth, or did it become apparent later? Has it changed at all since you first observed it, either improving or worsening?

Document any responses to handling. Does your baby cry when you move the arm? Is there a particular position that seems more comfortable? These observations provide valuable information for the medical evaluation.

Questions to Ask Your Baby’s Medical Team

When discussing your baby’s arm weakness with healthcare providers, specific questions can help you understand what’s being assessed and what comes next.

About the Movement Pattern

Ask which specific nerves or structures might be affected based on the movement pattern observed. What does the physical examination show about reflexes and muscle tone? How does the medical team distinguish between nerve injury and fracture?

Request clarification about what the Moro reflex and other newborn reflexes reveal about your baby’s condition. Understanding which movements are present and which are absent helps you grasp the nature of the injury.

About Next Steps and Follow-Up

Find out what additional evaluation is recommended. Will your baby need imaging studies like X-rays or ultrasound? Is a referral to a pediatric neurologist, orthopedist, or other specialist planned?

Ask about the timeline for follow-up. When should you return for re-evaluation? What changes or improvements should you watch for? What signs would indicate the need to return sooner than planned?

Understanding brachial plexus injury diagnosis and treatment options helps you know what to expect as your baby’s care progresses.

What Happens Next in Evaluation and Diagnosis

The medical team will use several approaches to determine the cause and extent of your baby’s arm weakness.

Physical Examination and Reflex Testing

A thorough physical examination includes observing your baby’s spontaneous movements, testing reflexes, and gently moving the arm through its range of motion. The provider will assess muscle tone, look for areas of tenderness, and check for swelling or deformity.

The pattern of which movements are affected and which are preserved helps distinguish between different types and locations of injury. For example, preserved hand function with shoulder weakness suggests upper brachial plexus involvement, while a completely immobile arm might indicate more extensive nerve injury.

When Imaging or Specialist Referral May Be Needed

If a fracture is suspected, an X-ray can confirm the diagnosis and show the location and type of break. For suspected nerve injuries, imaging may be used to evaluate nearby bones, joints, or soft tissues and to rule out other causes. Some babies may also need specialist evaluation if weakness persists or appears severe.

Depending on the initial findings, your baby may be referred to specialists such as pediatric neurologists, orthopedic surgeons, or rehabilitation medicine physicians. These specialists have expertise in evaluating and managing birth-related nerve and bone injuries.

Early specialist involvement allows for appropriate monitoring and, if needed, early intervention that can support the best possible recovery.

Frequently Asked Questions

Getting the Answers You Need

If your baby’s arm looks weak, limp, painful, or different from the other arm after delivery, document what you notice and seek prompt medical evaluation. Ask the care team whether the pattern suggests a nerve injury, fracture, positioning-related weakness, or another cause, and request clear follow-up instructions so changes in movement, pain, swelling, or hand function are not missed.

This article is for educational and informational purposes only. It is not medical advice and cannot replace evaluation and guidance from qualified healthcare providers. If you notice arm weakness, pain, swelling, color change, poor feeding, breathing problems, or any concerning symptoms in your newborn, contact your pediatrician or seek immediate medical care. This article is also not legal advice. If you have questions about whether a birth injury may have been preventable, consider consulting an attorney who handles birth injury cases.