The human body protects itself with involuntary reflexes, like blinking your eyes to avoid incoming debris or lifting your hand to your face to deflect a snowball. Reflexes are your body's way of interacting with the world when there isn't time to consult the brain. You are born with these reflexes and your life experiences can sharpen or dull these spontaneous motions. Babies are born with a variety life-saving reflexes that disappear within a few months. One such involuntary motion is the startle reflex, otherwise known as the Moro Reflex, according to Children's Hospital of Wisconsin.
Dr. Moro
Dr. Ernst Moro was an Austrian pediatrician and physician in the early part of the 20th century. Dr. Moro was the first to recognize the startle reflex in babies. He was also famous for discovering that cow's milk was insufficient for human babies because it lacked a certain enzyme found in breast milk.
Action
When a baby is startled by a loud noise or senses that she is falling, she throws back her head, arches her back and extends her arms and legs. She curls her thumb and index finger together, resembling the letter C. She may let out a cry at this point. Suddenly, she jerks her limbs back toward her body, bending her elbows and knees, in a grasping motion. Wondertime references Douglas Vanderbilt, a developmental-behavioral pediatrician at Childrens Hospital Los Angeles, who says this reflex is a throwback to when humans were furrier. An infant who felt like she was falling reflexively grasped onto her mother's fur.
Duration
An infant develops this reflex while he is still in the womb and displays the reflex until he is 3 to 4 months old. The baby's brain and body matures until he no longer needs the Moro reflex. The reflex fades at the appropriate time in the baby's development, as the jerking motion of the reflex would likely interfere with a baby's attempts to sit, crawl or stand.
Diagnostic Tool
Physicians use the Moro reflex to measure an infant's nervous system. The doctor will lay an infant on a soft mat, lift the infant's head and shoulders a couple of inches from the mat while holding the baby's arms flexed next to her body. The doctor will suddenly let go, letting the baby's head and shoulders suddenly fall onto the mat while releasing the baby's arms to simulate a sense of falling. A healthy infant will fully extend, or adduct, both arms before fully abducting, or bringing them back in close to his chest. A healthy baby will also form the letter C with fingers on both hands. According to the University of Utah Health Sciences Library, a baby demonstrating absent or incomplete Moro reflexes is suffering from neurological disorders.
