Exploring the olfactory environment of premature newborns: a French survey of health care and cleaning products used in neonatal units.

AIM: To assess the main determinants of the newborn's nosocomial olfactory environment. METHODS: An electronic questionnaire was sent to 99 neonatal units in France. Senior nurses and/or physicians described the nature and use of skin care products (e.g. umbilical cord and skin disinfectants, adhesive removers), lubrications used for tubes positioning, disinfectants used to clean materials, hand hygiene products (e.g. alcohol-based hand rubs, soaps) and newborns' bath. RESULTS: Nine groups of products and 76 distinct commercial preparations were identified. Depending on their level of respiratory support, preterm newborns were estimated to be exposed to nosocomial odours (NO) an average of 1320-1800 times during their first month of life. During their whole hospital stay, newborns of 28 and 32 weeks of gestational age could be exposed to NOs products an average of 3448 and 2024 times, respectively. The use of these products varied among medical centres. Newborns were most frequently exposed to the odour of aqueous alcoholic solutions. CONCLUSIONS: Vulnerable preterm infants are daily exposed to multiple NOs most of them be considered as irritant for the nose. Minimizing infants' exposure to them would be beneficial. Future studies should describe the exact olfactory properties of the products considered essential for infant care and should assess their effects on the infant's well-being and development.

Long-lasting memory for an odor acquired at the mother's breast.

Whether neonatal odor memory can persist into toddlerhood and influence behaviors that tap processes related to cognition (attention and exploration), motivation (choice and consumption), and emotion (hedonic processing) remains under-researched. Using a quasi-experimental longitudinal design, we examined whether an odor experienced at the mother's breast can be retained at 7 and 21 months. The prescribed prophylactic use of a camomile-scented balm defined two groups: infants exposed (CaE) or never exposed (CaNE) to camomile odor. At 7 months, exploratory responses to three similar objects differing in odor (including camomile) were analyzed. At 21 months, three tasks were used to assess toddlers' (i) facial responses; (ii) exploratory responses to three similar, but differently odorized objects; and (iii) choices between two bottles carrying different odors. CaE infants displayed preferential responses for camomile odor at both ages in every task. In contrast, CaNE infants behaved either randomly or more negatively to camomile odor. This study indicates that early odor memories acquired during breastfeeding can be reactivated and influence behavioral processes until at least toddlerhood.

Emotional responses to odors in children with high-functioning autism: autonomic arousal, facial behavior and self-report.

Although emotional functioning is impaired in children with autism, it is unclear if this impairment is due to difficulties with facial expression, autonomic responsiveness, or the verbal description of emotional states. To shed light on this issue, we examined responses to pleasant and unpleasant odors in eight children (8-14 years) with high-functioning autism and 8 age-matched typically developing controls. Despite subtle differences in the facial actions of the children with autism, children in both groups had similar facial and autonomic emotional responses to the odors. However, children with autism were less likely than controls to report an emotional reaction to the odors that matched their facial expression, suggesting difficulties in the self report of emotional states.

Learning at the breast: preference formation for an artificial scent and its attraction against the odor of maternal milk.

Human newborns are known to display spontaneous attraction to the odor of human milk. This study aimed to assess whether the positive response to human milk odor can be explained by nursing-related learning, and whether it can be easily reassigned to a novel odor associated with nursing. Infants were exposed or not to a novel odor (camomile, Ca) during nursing, and tested on day 3-4 for their preference for camomile in comparison with either a scentless control (Exp. 1), a scented control (Exp. 2), or maternal milk (Exp. 3). Prior experience with Ca modified the newborns' responses. While the Ca odor became more attractive than a scented control in the Ca-exposed group, the Ca-non-exposed group did not differentiate either stimulus. In Exp. 3, the Ca-non-exposed group preferred the milk odor to the Ca odor, whereas the Ca-exposed group displayed on average equal attraction to both stimuli. Thus, a novel odor can be learned at the breast, and gain similar attractive power than the odor of mother's milk. In sum, reinforcements related with the early episodes of breastfeeding mediate the rapid development of novel odor preferences in human infants.

Human newborns prefer human milk: conspecific milk odor is attractive without postnatal exposure.

Behavioral responses of 3- to 4-day-old newborns to the odors of various human milk (HM) and formula milk (FM) were examined in paired-choice tests. When both stimuli were nonfamiliar, breast-fed, as well as bottle-fed, infants oriented their head and mouthed more vigorously to HM than to FM. When breast-fed infants were exposed to nonfamiliar HM along with the familiar FM, their head-turning responses were undifferentiated although they mouthed more frequently to the human stimulus. When nonfamiliar HM and familiar FM were equalized in intensity, nonfamiliar HM again elicited more head orientation and mouthing responses. These results demonstrate that the odor of HM is more attractive to human newborns than FM and that this preference is independent of postnatal feeding experience.

Olfactory stimulation prevents apnea in premature newborns.

OBJECTIVE: Methylxanthines and doxapram are currently used to treat apnea of prematurity but are not fully effective and often present undesirable side effects. The present study examines whether exposure to an odor known to modulate the infant's respiratory rate could reduce the frequency of apneic spells. METHOD: Fourteen preterm newborns born at 24 to 28 gestational weeks presenting recurrent apnea despite caffeine and doxapram therapy were exposed to a pleasant odor diffused during 24 hours in the incubator. Efficiency of the olfactory treatment was judged by comparing frequency and severity of apneas occurring during the day of odorization with that observed the day before (baseline) and the day after (posttreatment control). Apnea was defined as any complete cessation of breathing movements for >20 seconds, or less if associated with hypoxia or bradycardia. RESULTS: Concerning all types of apneas, a diminution of 36% was observed and seen in 12 of 14 infants. Apneas without bradycardia were reduced (44%) during the day with odorization, and this diminution affected all the infants. The frequency of apnea with moderate bradycardia (heart rate between 70 and 90 beats per minute) was maintained while the frequency of apnea associated with severe bradycardia (heart rate <70 beats per minute) decreased strongly (45%) and affected all the infants. No side effects were observed. CONCLUSION: The introduction of a pleasant odor in the incubator is of therapeutic value in the treatment of apneas unresponsive to caffeine and doxapram.