Neonatal Responsiveness to the Odor of Amniotic and Lacteal Fluids: A Test of Perinatal Chemosensory Continuity

Abstract

The head-orientation response of 2- and 4-day-old breast-feeding neonates was studied in paired-choice odor tests. Three tests were conducted on day 2 (amniotic fluid [AF] versus Colostrum; AF versus Control; Colostrum versus Control) and on day 4 (AF versus Milk; AF versus Control; Milk versus Control). At 2 days, both AF and Colostrum elicited positive orientation when presented simultaneously with the control stimulus, indicating that both odors were detectable to the infants. However, no differential responses were noted when AF and colostrum were presented concurrently, suggesting that both of these substrates were treated as similar sensorily and/or hedonically. On day 4, the odors of AF and transitional milk elicited attraction responses when presented in competition with a control stimulus. When the odor of milk was presented simultaneously with the odor of AF, the former elicited longer head orientation. Thus, within the first 4 days of life olfactory selectivity changes from a null preference between cues carried in AF and in colostrum to a positive preference for cues carried in postamniotic odors, that is, breast milk. An additional experiment indicated that 3-day-old neonates orient longer toward the odor of their own AF than toward the odor of alien AF, showing that prenatal odors elicit selective responding for some time after birth. Altogether these results were interpreted as supporting the hypotheses that prenatal experience might influence the earliest odor preferences in the breast-feeding human neonate and that these preferences rapidly evolve according to postnatal experience.

Fetal Learning About Ethanol and Later Ethanol Responsiveness: Evidence Against “Safe” Amounts of Prenatal Exposure

“…At 4 days of age, the infants are still capable of discriminating the odors of amniotic fluid and maternal milk, but now they clearly show preferences for the milk. These results suggest that babies go through a period of transition in terms of their preference for biological chemosensory cues, from amniotic fluid to colostrum, and then to maternal milk (55,56). As mentioned, morphologic and histologic studies in mammals indicate that olfactory subsystems responsible for chemosensory perception start developing during early gestational stages.…”

Kangaroo Care (Skin Contact) Reduces Crying Response to Pain in Preterm Neonates: Pilot Results

“…Maternal presence per se, as differentiated from Kangaroo Care, may also have influenced pain responses because preterm infants who receive the familiar odor of their mother when having a heel stick performed show no increase in crying as compared to baseline levels (Goubet, Rattaz, Peirrat, Bullingere & Lequien, 2003). Maternal scents reduce post-heel stick crying in fullterm infants (Rattaz, Goubet & Bullinger, 2005), partially due to newborn recognition of maternal scent from the womb (Marlier, Schaal & Soussignan, 1998;Rangel and Leon, 1995). Future study with a cohort of infants who only experience maternal presence rather than the holding, containment, skin contact, heart beat, and rhythmic chest movement elements that comprise Kangaroo Care, may provide data as to the most effective way mothers may contribute to their infant's pain management.…”

Prenatal and Postnatal Flavor Learning by Human Infants

“…10 Within days of birth, human infants will orient toward the odor of their own amniotic fluid, which suggests that prenatal sensory experiences can bias the newborn's behaviors and preferences. 11,12 Moreover, the environment from which the newborn came, the amnion, contains compounds derived from flavors of foods eaten by the pregnant mother. 13,14 Such exposure to dietary transmitted flavors (eg, garlic, anise) in amniotic fluid has been shown to influence the newborn's facial, mouthing, and orienting responses to the flavor in the short-term.…”