Newborn jitteriness is characterized by involuntary, rhythmic movements. These movements are typically rapid, fine tremors that most often affect the chin or the extremities. It is generally a manifestation of normal physiological development in the first weeks of life. Understanding the difference between these benign tremors and more serious causes is important for proper parental response.
Why Normal Newborn Jitteriness Occurs
The majority of jittery movements observed in a newborn are a direct result of their immature central nervous system (CNS). The nerve pathways that control muscle activity are still developing their insulation and coordination, which can lead to temporary, unrefined signals being sent to the muscles. This immaturity often results in a fine tremor with a high frequency and low amplitude, particularly in the hands, arms, and lower jaw.
These non-pathological tremors are often triggered or intensified by external stimuli such as crying, being startled, or being cold. For example, the Moro reflex causes a baby to suddenly extend their arms and legs in response to a sudden noise or change in position. This reflexive response can sometimes manifest as a brief, shaky movement.
A key characteristic of normal newborn jitteriness is that the movements are transient and can be easily interrupted. Gently holding the affected limb or swaddling the baby will typically stop the tremor immediately. If the movement ceases when the baby is comforted or the limb is held still, it indicates a benign tremor rather than a neurological event.
How to Tell the Difference Between Jitters and Seizures
Differentiating between normal jitters and a true seizure relies on the movement’s characteristics. The most definitive practical test involves physical intervention: a benign tremor will stop if the parent gently restrains or flexes the shaking limb. In contrast, a seizure involves abnormal electrical discharge in the brain, resulting in movements that are continuous and cannot be stopped by simple physical restraint.
The visual appearance of the movement also provides important clues. Jitteriness is described as a fine, rapid, and rhythmic oscillation, similar to a sustained shiver. Seizures, especially in newborns, are often subtle, involving coarse, jerky movements. They can also present as rhythmic movements like lip smacking, bicycling motions of the legs, or eye deviation where the eyes fixate or move rhythmically in one direction.
Seizures are commonly associated with changes in the baby’s autonomic function, which controls involuntary body processes. During a seizure, there may be noticeable changes in heart rate, breathing rate, or oxygen saturation. Normal jitteriness, however, does not involve these disturbances or changes in the baby’s gaze.
Medical Causes of Newborn Tremors
When tremors are not easily stopped by restraint, they may indicate an underlying pathological issue. The most frequent metabolic cause of pathological jitters is hypoglycemia, or low blood sugar. Newborns, particularly those who are born small or large for gestational age, or those whose mothers have diabetes, can struggle to regulate their blood glucose levels after birth.
Another important metabolic cause is hypocalcemia. Calcium is important for muscle and nerve function, and low levels can lead to increased neuromuscular excitability, manifesting as tremors or muscle twitches. This is sometimes seen in premature or low birth weight babies, or those with certain hormonal imbalances.
Tremors can also be a significant symptom of Neonatal Abstinence Syndrome (NAS), which occurs when a newborn withdraws from substances the mother used during pregnancy, such as opioids or nicotine. These tremors are typically more severe, persistent, and are accompanied by other signs of CNS irritability, like irritability, high muscle tone, and difficulty feeding. The sudden lack of the substance after birth disrupts the baby’s system.
Infections, such as sepsis or meningitis, can also present with jitteriness, although this is usually in conjunction with other symptoms of illness. In these cases, the tremors are a sign of systemic distress. Conditions like hyperthyroidism or vitamin D deficiency have also been linked to persistent jitteriness beyond the first week of life.
Warning Signs and When to Seek Medical Care
Parents should seek prompt medical advice if the baby’s shaking cannot be stopped by gently holding the affected limb or by comforting the baby. Any tremor that is persistent, occurs when the baby is calm, or appears to be worsening should be evaluated immediately.
Urgent attention is necessary if the tremors are accompanied by other concerning physical signs:
- A fever of 100.4°F (38°C) or higher
- Difficulty waking the baby, or profound lethargy
- Poor feeding
- A blueish tint to the lips or skin
- Severe trouble breathing
If the movements display seizure-like characteristics, such as coarse jerking, eye deviation, or subtle rhythmic motions like lip smacking, contact a medical professional right away. Any abnormal behavior in a newborn less than one month old requires a medical assessment.