The following neonatal reflex disappears by what age
**Core Concept**
The question is testing the knowledge of neonatal reflexes and their disappearance timeline. Neonatal reflexes are automatic responses to specific stimuli that are present at birth and play a crucial role in the development and maturation of the nervous system. These reflexes gradually disappear as the infant grows and develops.
**Why the Correct Answer is Right**
The correct answer refers to the "Moro reflex" or "startle reflex", which is one of the most prominent neonatal reflexes. It is characterized by a sudden extension of the arms and legs, followed by a flexion of the elbows and knees, in response to a sudden loss of support or a loud noise. The Moro reflex disappears around 4-6 months of age as the infant develops better motor control and coordination.
**Why Each Wrong Option is Incorrect**
**Option A:** The "Gag reflex" or "pharyngeal reflex" is a protective reflex that helps to prevent foreign objects from entering the airway. It is present from birth and does not disappear with age.
**Option B:** The "Rooting reflex" is another neonatal reflex that helps the infant to find the nipple and breast. It disappears around 4-6 weeks of age, not later.
**Option C:** The "Sucking reflex" is a fundamental reflex that helps the infant to feed. It is present from birth and does not disappear with age.
**Clinical Pearl / High-Yield Fact**
Neonatal reflexes are essential for assessing the neurological development and maturation of the infant. A delay or absence of these reflexes can indicate neurological problems or developmental delays.
**Correct Answer:** D.