Moro reflex - wikipedia Moro reflex Play media 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 ) Play media 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 : spreading out the arms ( abduction ) unspreading the arms ( adduction ) 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, and is believed to be the only unlearned fear in human newborns. Contents 1 Interpretation 2 History 3 Function 4 References 5 External links Interpretation 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 ). 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. 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. History The reflex was first described in western medicine by Austrian pediatrician Ernst Moro ( 1874 -- 1951 ). Function The Moro reflex may have developed in human evolution to help the infant cling to their mother while she carried them around all day. If the infant lost their balance, the reflex caused the infant to embrace their mother and regain their hold on the mother 's body. References Jump up ^ Fletcher, Mary Ann ( 1998 ). Physical Diagnosis in Neonatology. Philadelphia : Lippincott - Raven. p. 472. ISBN 978 - 0397513864. Retrieved 7 February 2013. Jump up ^ 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. Jump up ^ Berk, Laura E. ( 2009 ). Child Development ( 8th ed. ). Boston : Pearson. ISBN 978 - 0 - 205 - 61559 - 9. Retrieved 7 February 2013. External links Medline Plus : Moro reflex Video of the Moro Reflex from the University of Utah ( Google Video ) Pathologic Moro Reflex in an adult following acute demyelinating lesion of unknown origin in medulla oblongata ( Neurology ) Nervous system physiology : neurophysiology - reflex Cranial nerve midbrain : Pupillary light reflex Accommodation reflex pons / medulla : Jaw jerk reflex Corneal reflex Caloric reflex test / Vestibulo - ocular reflex / Oculocephalic reflex Pharyngeal ( gag ) reflex Stretch reflexes upper limb : Biceps reflex C5 / C6 Brachioradialis reflex C6 Triceps reflex C7 / C8 lower limb : Patellar reflex L2 - L4 Ankle jerk reflex S1 / S2 Plantar reflex L5 - S2 Primitive reflexes Galant Gastrocolic Grasp Moro Rooting Stepping Sucking Tonic neck Parachute Superficial reflexes Abdominal reflex Cremasteric reflex Lists general alphabetical by organ Cardiovascular Bainbridge reflex Bezold - Jarisch reflex Coronary reflex Diving reflex Oculocardiac reflex Baroreflex Reflex bradycardia Reflex tachycardia Respiratory Churchill - Cope reflex Other Acoustic reflex H - reflex Golgi tendon reflex Optokinetic Startle reaction Withdrawal reflex ( Crossed extensor reflex ) Symmetrical tonic neck reflex Retrieved from `` https://en.wikipedia.org/w/index.php?title=Moro_reflex&oldid=801575821 '' Categories : Reflexes Obstetrics Pediatrics Hidden categories : All articles with unsourced statements Articles with unsourced statements from June 2009 Articles with unsourced statements from April 2015 Articles containing video clips Talk Contents About Wikipedia Čeština Dansk Deutsch Español Français Hrvatski Italiano עברית Nederlands 日本 語 Norsk nynorsk Polski Português Српски / srpski 中文 Edit links This page was last edited on 20 September 2017, at 14 : 44. About Wikipedia

Question: when does a baby lose their startle reflex
Answer: 3 or 4 months of age