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.