When a newborn baby is laid face up on a surface and its head is lifted slightly then dropped back, (cradled safely, of course!) the baby will fling its arms and legs outwards then immediately draw them back towards the body in a grasping motion, exhibiting the innate behavior known as the Moro reflex. The Moro reflex can be seen even in premature babies, and it disappears by four to five months of age.
No one enjoys frightening a small baby, but physicians perform this reflex test, along with others in a neonatal examination, to determine the health of the newborn’s brain, spinal cord and peripheral nerves. A slightly older baby may begin to cry with this response is elicited, but most babies are easily soothed afterwards and the experience doesn’t seem to cause any permanent fears or aversions. Most newborns don’t seem to notice their own body movements during this reaction.
The startle response is similar, but different. An infant may respond to a loud noise or other sudden stimulus by flinging its arms and legs out in a rigid, jerky manner, with a simultaneous jerking of the trunk and head. The baby also usually exhibits a recognizably startled facial expression and cries out sharply. This type of fear reaction may not be as easily soothed as one elicited from reflex. The startle reaction is normal and is retained throughout adulthood.
Absence of the Moro reflex, or a reflex response on one side only, may indicate a problem. Causes for an abnormal Moro reflex response range from birth-related shoulder injuries to profound neurological defects. Retention of the Moro reflex past the age of five months may indicate serious health issues, such as congenital defects of the brain or spine. Individuals with cerebral palsy may exhibit the Moro reflex into adulthood.
Other normal newborn reflexes include the Babinski reflex, the rooting reflex and the grasping reflex, among others. Vulnerable but not entirely helpless, a newborn baby is “preprogrammed” to respond to life’s demands before leaving the womb.