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The Moro reflex in a four-day-old infant: 1) the reflex is initiated by pulling the infant up from the floor and then releasing him; 2) he spreads his arms; 3) he pulls his arms in; 4) he cries (10 seconds)
Moro reflex while sleeping

The Moro reflex is an infantile reflex normally present in all infants/newborns up to 3 or 4 months of age as a response to a sudden loss of support, when the infant feels as if it is falling. It involves three distinct components:

  1. spreading out the arms (abduction)
  2. pulling the arms in (adduction)
  3. crying (usually)

The primary significance of the Moro reflex is in evaluating integration of the central nervous system. It is distinct from the startle reflex,[1] and is believed to be the only unlearned fear in human newborns.[citation needed]



The Moro reflex may be observed in incomplete form in premature birth after the 28th week of gestation, and is usually present in complete form by week 34 (third trimester)[citation needed]. Absence or asymmetry of either abduction or adduction is abnormal, as is persistence of the reflex in older infants, children and adults. Absence indicates a profound disorder of the motor system or a generalised disturbance of the central nervous system. An absent or inadequate Moro response on one side is found in infants with hemiplegia, brachial plexus palsy, or a fractured clavicle. Persistence of the Moro response beyond 4 or 5 months of age is noted only in infants with severe neurological defects.[2] In individuals with cerebral palsy, persistence and exacerbation of this reflex is common.

The Moro reflex is impaired in the early stage of kernicterus and it is absent in the late stage of kernicterus.


The reflex was first described in western medicine by Austrian pediatrician Ernst Moro (1874–1951).


The Moro reflex may be a survival instinct to help the infant cling to its mother. If the infant lost its balance, the reflex caused the infant to embrace its mother and regain its hold on the mother’s body.[3]


  1. ^ Fletcher, Mary Ann (1998). Physical Diagnosis in Neonatology. Philadelphia: Lippincott-Raven. p. 472. ISBN 978-0397513864. Retrieved 7 February 2013.
  2. ^ Samuels, Martin A.; Ropper, Allan H. (2009). "Normal Development and Deviations in Development of the Nervous System". Adams and Victor's Principles of Neurology (9th ed.). New York: McGraw-Hill Medical. ISBN 9780071499927. Retrieved 7 February 2013.
  3. ^ Berk, Laura E. (2009). Child Development (8th ed.). Boston: Pearson. ISBN 978-0-205-61559-9. Retrieved 7 February 2013.

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