Myristic acid in amniotic fluid produces appetitive responses in human newborns.

BACKGROUND: A mixture of eight fatty acids (lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, elaidic acid, and linoleic acid) that are contained in human amniotic fluid, colostrum, and milk produces appetitive responses in newborns, suggesting the existence of a transition of sensorial cues that guide newborns to the maternal breast. OBJECTIVE: To explore the ability of each of these eight fatty acids individually to produce appetitive responses in newborns. METHODS: The study included 12 healthy human newborns<24h after birth. Using a longitudinal design, cotton swabs that were impregnated with each of the eight fatty acids and control substances (i.e., vehicle, saline, and vanilla) were placed approximately 1cm from the newborns' nostrils for 30s. Positive responses that were suggestive of acceptance included appetitive movements (i.e., suckling) and sniffing that were directed toward the cotton swab. Lateral movements of the head away from the swab were considered negative responses. Remaining stationary with no changes in facial expressions was considered indifference. RESULTS: Compared with controls (i.e., vehicle, saline, and vanilla) and the other fatty acids tested, myristic acid produced the longest duration of positive facial responses (suckling and sniffing). No significant differences in negative facial responses were observed in response to the odoriferous stimuli. No reactions that were suggestive of disgust were observed. CONCLUSION: A complex combination of stimuli, including the odor of myristic acid, may integrate sensory cues that guide newborns to the maternal breast.

Amniotic fluid elicits appetitive responses in human newborns: fatty acids and appetitive responses.

In humans, maternal cues guide newborns to the maternal breast, and transitional cues may be present in maternal-fetal fluids. The aim of the present study was to determine the consistent presence of sensorial cues in three maternal-fetal fluids--amniotic fluid, colostrum, and milk--and test the ability of these cues to produce appetitive responses in newborns. In the analytical study, gas chromatography-mass spectrometry (GC-MS) detected eight fatty acids consistently present in the amniotic fluid, colostrum, and milk from 12 healthy volunteers, but we do not find a mammalian pheromone, identified in another mammalian species (rabbits), in another 30 volunteers. In the behavioral study, we explored the ability of amniotic fluid or its fatty acids to produce appetitive responses in 19 human newborns <24 hr after birth. Exposure to swabs impregnated with amniotic fluid or an artificial fatty acid mixture produced a longer duration of facial reactions that suggested appetitive (sucking) movements compared with respective vehicles (i.e., propylene glycol or centrifuged amniotic fluid with a low fatty acid content verified by GC-MS). We conclude that the fatty acids contained in amniotic fluid may constitute a transitional sensorial cue that guides newborns to the maternal breast.