A mother drops her three-month-old infant's head into extension. This action would MOST likely elicit which reflex?

• A. Moro
• B. Grasp
• C. Tonic labyrinthine
• D. Extensor thrust

Answer: (A)

The Moro reflex is the infant’s startle response to a sudden loss of support or abrupt change in position. When the head is dropped into extension, this abrupt movement feels like a fall, triggering the arms to extend outward and then come back toward the body in a embracing pattern, often with crying. This reflex is present at birth and typically integrates by about four to six months, so a three-month-old would exhibit it. Other reflexes don’t fit this scenario: the grasp reflex requires tactile contact with the palm to produce finger flexion, and the tonic labyrinthine reflex depends on sustained head position relative to gravity to shift overall muscle tone rather than producing a quick startle. Extensor thrust isn’t the typical response to a sudden head drop.