Olfactory reflexes in the newborn infant.

Clinical responses to peppermint odor were observed in 100 healthy term and preterm infants during active sleep on two successive days. Thirty-six asphyxiated term infants and three infants with holoprosencephaly also were tested. Olfactory reflexes were regularly elicited in normal infants after 32 weeks' gestation, but some premature infants as young as 28 weeks also responded. Responses included initiation of sucking and arousal-withdrawal. Habituation occurred after two or three trials. A Moro response was seen only in a few asphyxiated infants; loss of olfactory reflexes appeared to parallel suppression of brainstem reflexes. Olfactory reflexes are useful in excluding cerebral malformations associated with agenesis of the olfactory bulbs.