Newborns' Bodies: Why They're Stiff And What's Normal

It is not uncommon for newborns to be stiff, and there are many reasons why this may be the case. Stiffness in newborns can be caused by anything from a simple startle reflex to a more serious underlying condition. In most cases, it is not a big deal, but in some cases, stiffness can be a sign of a birth injury or other medical condition.

Babies may stiffen their bodies when they are excited, frustrated, or upset, or when they are picked up or put into a car seat or high chair. They may also stiffen their legs and arms when they get a fright from a loud noise or a sudden movement. This is known as the startle, or Moro, reflex and is usually nothing to worry about.

However, if a baby's muscles are always stiff, it could be a sign of an underlying illness such as hypertonia, or stiff baby syndrome. Hypertonia is caused by an injury to the brain or spinal cord and results in too much muscle tone, making the baby's muscles stiff and hard to move. Other possible causes of stiffness include cerebral palsy, Erb's palsy, shoulder dystocia, kernicterus, and infantile spasms.

If you are concerned about your baby's stiffness, it is important to seek medical advice.

Hypertonia, or stiff baby syndrome, is a condition that makes a baby's muscles stiff and hard to move

Hypertonia, or stiff baby syndrome, is a condition that affects a baby's muscle tone, causing their muscles to become stiff and hard to move. It is characterised by too much muscle tone, which results in stiffness and rigidity in the baby's muscles, particularly when they are being held. This stiffness can make it difficult for newborns to move their arms and legs, and they may have trouble with mobility and flexing.

There are two types of hypertonia:

• Dystonic hypertonia: The baby is stiff all the time, whether they are moving or not. This type is marked by muscles that rarely or never relax. Dystonic hypertonia is characterised by involuntary, repetitive muscle contractions.
• Spastic hypertonia: The baby's muscles tighten often, such as when they are picked up. This type is marked by muscle spasms and exaggerated reflexes in response to movement.

The muscle stiffness in hypertonic infants can range from mild to severe and can sometimes go away on its own without causing concern. In other cases, hypertonia may be caused by birth trauma or another underlying condition.

Some possible causes of hypertonia include:

• Cerebral palsy: This is a medical condition that can develop due to brain damage during childbirth, specifically when the baby experiences reduced blood flow to the brain, resulting in oxygen shortage and damage to the brain's motor control centres.
• Strokes: Neonatal strokes can occur when a baby doesn't get enough oxygen while travelling through the birth canal.
• Head trauma: A head injury, such as one inflicted by forceps during delivery, can damage the brain and cause hypertonia.
• Brain tumours: Tumours are abnormal cell growths that may affect the part of the brain that controls movement, leading to hypertonia.
• Exposure to harmful chemicals: If a baby comes into contact with a chemical that damages the brain or spinal cord, they may develop hypertonia.
• Kernicterus: This is a type of preventable brain injury that occurs due to untreated jaundice in newborn babies. If jaundice goes untreated, it can lead to a build-up of bilirubin in the blood, resulting in brain injury.

Hypertonia can lead to long-term health issues if left untreated. These issues can include delays in motor development, muscle stiffness, and learning or behavioural challenges. Treatment options for hypertonia include physical therapy, medication, and in some cases, surgery.

It is normal for babies to stiffen their bodies when they get excited or frustrated

It is perfectly normal for babies to stiffen their bodies when they get excited or frustrated. This is usually nothing to worry about, and is simply a natural reflex.

Babies are very flexible, and can often pull their feet up close to their face. However, hypertonic infants, or babies with stiff baby syndrome, are unable to do this. Stiff baby syndrome, or hypertonia, is a condition where a newborn has an excessive amount of muscle tone, leading to stiffness or rigidity in their muscles. This can be caused by various factors, such as brain injury, metabolic disorders, and genetic conditions.

There are two types of hypertonia:

• Dystonic hypertonia: The baby is stiff all the time, whether they are moving or not. Dystonic hypertonia is marked by muscles that rarely, if ever, relax.
• Spastic hypertonia: The baby’s muscles frequently tighten, for example, whenever you pick the baby up. This type of hypertonia is marked by muscle spasms and exaggerated reflexes in response to movement.

The muscle stiffness in hypertonic infants can range from mild to severe. Sometimes, it goes away on its own and isn’t a cause for concern. However, if your baby is abnormally stiff, there is a small possibility that this is a symptom of a more serious underlying problem.

Stiffening can also be caused by pain, discomfort, or overstimulation

While it is normal for newborns to stiffen their bodies, for instance, when they are excited or frustrated, there are some cases where stiffening can be caused by pain, discomfort, or overstimulation.

Babies can experience pain and discomfort for various non-serious reasons and may appear stiff. For example, they may stiffen their bodies during or after feeding, especially if they are experiencing discomfort from gas.

In some cases, if a baby is overstimulated or overwhelmed, they might arch their back and become stiff. Similarly, sleeping in a particular position can cause a baby to seem stiff upon waking, similar to adults who sleep in an awkward position.

Babies can also stiffen their bodies when they are upset, frustrated, or angry. Angry babies often stiffen their legs and arms, turn red, and appear tense.

Babies may also stiffen their legs and arms when picked up due to the Moro reflex

It is normal for newborns to stiffen their arms and legs when picked up due to the Moro reflex, also known as the startle reflex. This is a natural reflex for newborns, where they react to loud sounds or sudden movements by throwing back their heads, extending their arms and legs, crying, and then pulling their arms and legs back in. The Moro reflex is typically most noticeable in newborns and disappears by four to six months of age at the latest.

In rare cases, these movements may be a sign of a more serious condition, such as infantile spasms, a rare type of epilepsy, or cerebral palsy, a congenital muscle disorder. If you are concerned about your baby's stiffness, it is important to seek advice from a healthcare professional.

If stiffness is accompanied by other symptoms, it may be a sign of an underlying condition

While stiffness in newborns is common and often harmless, it can sometimes be a sign of an underlying condition.

Hypertonia

Stiffness in newborns can be a symptom of hypertonia, a condition where a baby has an abnormally high muscle tone, causing stiffness and rigidity in their muscles. Hypertonia is caused by an injury or condition affecting the function of the central nervous system. The muscles are chronically contracted, making it difficult for the baby to move them.

Babies with hypertonia may have trouble walking, balancing, and letting go of objects. They may also experience pain or soreness in their muscles, as well as jerking or twitching movements. In severe cases, joints can freeze in place, causing permanent tightening of the muscles, tendons, skin, and tissues.

There are two types of hypertonia:

• Spastic hypertonia: Exaggerated reflexes and muscle spasms that increase with movement.
• Dystonic hypertonia: Muscle stiffness that remains the same whether the baby is moving or still.

Cerebral Palsy

Cerebral palsy is a medical condition that can develop due to brain damage during childbirth, often caused by reduced blood flow to the baby's brain. This lack of oxygen damages the part of the brain that controls muscle movement, resulting in muscle stiffness, rigidity, and spasticity.

Kernicterus

Kernicterus is a type of brain injury that occurs due to untreated jaundice in newborn babies. Jaundice is common, affecting 60-80% of infants in the United States, and is usually harmless. However, if left untreated, it can lead to kernicterus, causing muscle stiffness and spasms, fever, and unusual eye movements.

Infantile Spasms

Infantile spasms are a rare type of childhood epilepsy affecting approximately 1 in 2,000 infants and children in the US each year. They can cause permanent changes to a child's developing brain if not treated early. During an infantile spasm, a baby may stiffen and extend their arms while scrunching up their knees or bending their neck forward.

Other Conditions

Stiffness in newborns can also be a sign of other underlying conditions, such as strokes, head trauma, brain tumors, exposure to harmful chemicals, Erb's Palsy, or shoulder dystocia.

If you are concerned about your baby's stiffness, it is important to seek medical advice. A healthcare provider will be able to examine your baby, review their medical history, and determine if any underlying conditions are present.

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