A nurse is assessing a 2-day-old newborn's primitive reflexes. Which finding would indicate a normal Moro reflex?

The Moro reflex, often described as a startle response, is a normal primitive reflex present in newborns. It is a critical component of the neurological assessment because its presence, symmetry, and quality provide insight into the integrity of the infant's central nervous system. The reflex is typically elicited by a sudden change in the infant's head position relative to the trunk, such as allowing the head to drop back slightly when the infant is in a semi-sitting position. A normal, complete Moro reflex follows a specific two-phase pattern.

In the first phase, the newborn responds by symmetrically extending and abducting the arms, with the fingers fanning out. This is immediately followed by the second phase, where the arms flex and adduct in a clasping motion back toward the body. The infant may also cry. Option 2 perfectly describes this sequence of extension and abduction followed by flexion and adduction, making it the correct finding for a normal Moro reflex.

The clinical significance of this reflex cannot be overstated. According to research on primitive reflex responses, the absence of the Moro reflex during the neonatal period is a highly diagnostic finding that can indicate a variety of compromised conditions, such as severe birth asphyxia or significant central nervous system injury ^[1]. An asymmetric response, where one arm moves differently from the other, may suggest a brachial plexus injury or a fracture of the clavicle or humerus on the side with diminished movement. The reflex normally integrates and disappears by 4 to 6 months of age. Its persistence beyond this time is an abnormal finding that warrants further evaluation for neurological dysfunction.

The other options describe different primitive reflexes that are assessed separately during a newborn examination. Distinguishing between these reflexes is a common focus in NCLEX-RN questions.

Option 1 describes the rooting reflex. When the infant's cheek is stroked, the normal response is for the infant to turn the head toward the stimulated side and open the mouth. This reflex is essential for feeding, as it helps the newborn locate the nipple.

Option 3 describes the palmar grasp reflex. When an object or the examiner's finger is placed in the infant's palm, the normal response is a strong, tight grasp. This reflex is mediated by a spinal reflex mechanism and is under the regulatory control of nonprimary motor areas through spinal interneurons ^[1]. Its absence can also have diagnostic significance related to neurological or musculoskeletal issues.

Option 4 describes the Babinski reflex. When the sole of the foot is stroked from the heel up the lateral aspect and across the ball of the foot, the normal newborn response is dorsiflexion of the great toe and fanning of the other toes. The extension of the leg on the same side is not a component of this reflex. The plantar grasp reflex, a related but distinct response, involves the toes curling downward to grasp an object placed against the sole, and is also of great clinical significance, particularly for the detection of spasticity ^[1].