Juanico and Pérez del Pulgar Marx1 described in 1955 a new reflex in newborn infants, hereafter called the Pérez reflex, which seems to have aroused little attention. We have been able to confirm many but not all observations of the Spanish authors.
The reflex is elicited with the baby lying in prone position on a hard surface, e. g., an examination table or mattress, or held face down on the examiner's hand. Using moderate pressure, the examiner runs his index finger or thumb along the spine from the pelvis upward to the neck.
In response to this stimulus, Juanico and Pérez list the following reactions:
flexion of the lower extremities
lordosis of the spine, with elevation of the pelvis
flexion of the upper extremities, with elevation of the head
strong cry, leading in many cases to glottic spasm with apnea and occasional cyanosis
VOLLMER H. A New Reflex in Young Infants. AMA Am J Dis Child. 1958;95(5):481-484. doi:10.1001/archpedi.1958.02060050485004