Observing a newborn’s leg or chin trembling—often described as jitters or tremors—is a common concern for parents. These involuntary, shaky movements are frequently seen in the first weeks of life. While most episodes are harmless, it is important to understand the distinction between these normal, temporary jitters and movements that signal a serious underlying health concern. This knowledge helps parents provide appropriate care and know precisely when to seek medical attention for their baby.
Why Newborn Shaking Is Often Normal
The most frequent reason for a newborn’s jitteriness is the immaturity of the central nervous system (CNS). The nerve pathways that send signals between the brain and the body are still developing during the early weeks. This developmental stage means the newborn’s system has less control over motor responses, leading to exaggerated or shaky movements when stimulated. These tremors are often rapid, rhythmic, and occur equally on both sides of the body, distinguishing them from more concerning movements.
Jitters are often triggered by external factors. The startle reflex, also known as the Moro reflex, can cause a sudden extension of the arms and legs followed by a tremor, usually in response to a loud noise or abrupt change in position. Changes in the baby’s environment, such as being unwrapped, transitioning from sleep to wakefulness, or feeling cold, can also provoke a temporary tremor. Such physiological tremors typically subside on their own as the nervous system gains maturity, usually by the age of one or two months.
How to Differentiate Between Jitters and Seizures
The most practical way to differentiate a benign jitter from a seizure is the restraint test. Normal jitteriness, which is essentially an exaggerated tremor, will stop immediately if the parent gently holds, flexes, or restrains the affected leg or arm. Seizure activity, however, is caused by abnormal electrical discharge in the brain and will continue regardless of whether the limb is held. This simple intervention is a powerful diagnostic tool that can provide immediate reassurance.
Jitters are typically fine, rapid, and have a consistent “to and fro” pattern, resembling a tremor. Seizures, particularly clonic seizures in newborns, are often described as coarser, jerkier movements. They may have a distinct fast and slow component, or they may involve only one side of the body. True seizure activity is often accompanied by other signs not seen with normal jitters, including dramatic alterations in heart rate, breathing, or a change in skin color.
Abnormal eye movements are another significant indicator of a seizure. Seizures can present with ocular phenomena such as fixed eye deviation, eye fluttering, or rapid blinking. Movements like lip smacking, sucking, or pedaling motions of the legs can also be subtle manifestations of seizure activity in a newborn. If the movement is accompanied by any of these non-movement-related symptoms, it is highly suggestive of a more serious neurological event.
Serious Medical Causes of Tremors
While most newborn jitters are benign, persistent or non-stop tremors can be a symptom of underlying pathological conditions. Hypoglycemia, or low blood sugar, is a common metabolic cause that requires immediate medical attention. Hypoglycemia can manifest as jitteriness, lethargy, or a poor suck in at-risk infants, such as those born to mothers with diabetes. The lack of adequate glucose can trigger seizure activity and potential neurological injury if not quickly corrected.
Another metabolic disturbance is hypocalcemia. Calcium is necessary for proper nerve conduction, and a deficit can cause symptoms like jitteriness, muscle jerking, and even seizures. Neonatal Abstinence Syndrome (NAS), which results from in-utero exposure to certain substances, also commonly presents with tremors, excessive irritability, and a characteristic high-pitched or shrill cry. The tremors associated with NAS can be severe and prolonged.
Other serious causes are related to the central nervous system itself, such as infection or injury. Neonatal seizures can be caused by conditions like hypoxic-ischemic encephalopathy (HIE), which is brain injury due to lack of oxygen or blood flow, or a CNS infection such as meningitis. In these cases, the tremors are a sign of a distressed brain and demand immediate evaluation. The presentation of these tremors is usually more severe and persistent than normal jitteriness.
Urgent Red Flags and When to Call the Doctor
Immediate medical attention is necessary if a baby’s shaking does not stop when the affected limb is gently held or repositioned. Any shaking accompanied by a significant change in the baby’s overall state should be treated as an emergency.
Specific red flags require urgent assessment. These include a fever of 100.4°F (38°C) or higher in an infant under three months of age, which can signal a serious infection. A baby who is unusually sleepy, difficult to wake up, or lethargic requires urgent assessment. Poor feeding, a weak suck, or a refusal to eat should also prompt a call to the doctor, as these can be signs of metabolic or infectious issues. Respiratory distress, indicated by rapid breathing over 60 breaths per minute, wheezing, grunting, or a bluish or gray tint to the skin, requires immediate emergency services.