Seeing a baby shake often causes immediate parental concern. These sudden movements can be confusing, making it difficult to determine if they are a normal part of development or a sign of a serious underlying issue. Understanding the difference between harmless, transient jitters and more concerning episodes is necessary for recognizing when a pediatrician’s help is needed.
Understanding Benign Newborn Tremors
The most frequent cause of shaking in a new baby is the immaturity of their developing nervous system. A newborn’s neural pathways are not yet fully controlled, leading to involuntary movements often called transient tremors or jitters. These harmless, quick movements typically present as fine, rapid shaking of the chin, lower lip, or extremities.
Jitters are frequently observed when the baby is upset, crying, overstimulated, hungry, cold, or transitioning between sleep states. This rhythmic oscillation distinguishes it from the jerky movements of a seizure. As the baby’s central nervous system matures, usually within the first month or two of life, these tremors naturally subside.
Another normal movement is the Moro reflex, the baby’s startle response to a sudden change in position or unexpected noise. During this involuntary action, the infant quickly extends their arms and legs outward before bringing them back in, sometimes accompanied by a cry. This reflex is present in healthy newborns and usually disappears by four to six months of age.
How to Distinguish Jitters from Seizures
Differentiating between a benign jitter and a seizure can be accomplished with a simple physical maneuver. A jitter, or tremor, can typically be stopped by gently restraining or repositioning the affected limb. Holding the limb still or flexing it will cause the benign movement to cease immediately. If the movement continues despite the attempt to stop it, the event is more likely a seizure and requires immediate medical evaluation.
The visual characteristics of the movement also offer clues for distinction. Jitters are fine, high-frequency, rhythmic, and symmetrical oscillations. In contrast, a seizure involves movements that are coarser and jerky. Seizures in newborns may also be subtle, manifesting as non-purposeful automatisms like repetitive lip smacking, fixed staring, or pedaling movements.
Jitters do not involve changes in the baby’s awareness or vital signs. During a seizure, the baby may exhibit autonomic changes, such as a change in heart rate or breathing pattern. Abnormal eye movements, like eye rolling or a tonic deviation of the gaze, are also suggestive of a seizure rather than a tremor.
Medical Conditions That Cause Shaking
Shaking movements can sometimes be a symptom of a systemic medical issue that needs immediate attention, particularly metabolic or infectious conditions. The most common metabolic problem in newborns is hypoglycemia, or dangerously low blood sugar. When glucose levels drop too low, it can cause neurological symptoms like jitteriness, tremors, lethargy, and a weak or high-pitched cry.
Hypoglycemia is a risk for infants born prematurely, those who are small or large for gestational age, or those born to mothers with diabetes. The infant may also show poor feeding, sweating, or a blue tint to the skin. Shaking can also be a physical response to poor temperature regulation, such as shivering from hypothermia, or it may be related to a systemic infection.
Another cause of pathological tremors is Neonatal Abstinence Syndrome (NAS), which occurs when a baby withdraws from substances exposed to in the womb. Characteristic signs of NAS include marked tremors, excessive high-pitched crying, irritability, and tight muscle tone. These withdrawal symptoms can also lead to feeding difficulties and, less commonly, seizures.
Red Flags and When to Call the Doctor
A movement that you cannot stop by holding the limb or changing the baby’s position is a serious red flag that warrants an immediate call to your pediatrician or emergency services. Any shaking episode accompanied by abnormal eye movements, such as a fixed stare, or localized to only one side of the body should be treated as an urgent concern. Seizures in newborns are often subtle, so you should be concerned if the movement is repetitive and lasts longer than 10 seconds.
You should also seek immediate medical attention if the shaking is paired with significant changes in the baby’s overall status, including difficulty breathing, a blue or pale discoloration of the skin, unresponsiveness, or extreme lethargy. A fever, especially in a newborn under twelve weeks old, combined with any type of tremor or seizure-like activity, requires prompt medical evaluation.