Primitive Reflexes — Moro, Startle, Positive Support, Stepping

What are the stimulus, response, and normal age of the Moro reflex?

• Stimulus:

  • Sudden head drop into extension

• Response:

  • Arms abduct

  • Fingers open

  • Arms then adduct

  • Cry may occur

• Normal age:

  • 28 weeks gestation to 5 months

What is the difference between Moro and startle reflexes?

• Moro:

  • Triggered by sudden head movement

  • Arms abduct with fingers open

• Startle:

  • Triggered by loud sudden noise

  • Similar response

  • Elbows remain flexed

  • Hands remain closed

What are the stimulus, response, and normal age of the positive support reflex?

• Stimulus:

  • Weight placed on balls of feet while upright

• Response:

  • Stiff extension of legs and trunk

• Normal age:

  • 35 weeks gestation to 2 months

What can persistent positive support interfere with?

• Standing

• Walking

• Weight shifting

• Balance reactions

• May contribute to plantar-flexion contractures

What are the stimulus, response, and normal age of the stepping reflex?

• Stimulus:

  • Supported upright

  • Feet placed on firm surface

• Response:

  • Reciprocal LE flexion and extension

• Normal age:

  • 38 weeks gestation to 2 months

What can persistent stepping reflex interfere with?

• Standing

• Walking

• Balance reactions

• Smooth coordinated reciprocal LE movement