Natural odour preferences of newborn infants change over time

At their first sucking contact, neonates prefer an unwashed breast to a washed one, but an amniotic fluid (AF)- treated breast over a "natural odour" breast. We examined the development of these neonatal olfactory preferences. On days 3–4 significantly more babies still selected their mother's unwashed breast ( n = 21) than the washed alternative ( n = 8). Preferences for natural breast odours were more pronounced for girls than boys. In a subsequent experiment comprising another 28 babies, the number of babies who selected a naturally scented ( n = 9) vs an AP-treated breast ( n = 19) on days 2–5 were not reliably different. However, babies who selected the natural breast had longer pre-test maternal contact and had spent more time breastfeeding. Ten babies who chose the AF breast in the latter experiment were tested in the same manner several days later; all preferred the naturally smelling breast. While preferences for AF fade after birth, responsiveness to natural breast odours may be enhanced by postnatal experience.     

Maternal breast milk odour induces frontal lobe activation in neonates: A NIRS study

We used near-infrared spectroscopy (NIRS) to examine differences in neonates' orbito-frontal cortical activation in response to the odours of maternal breast milk and formula milk in terms of changes in the oxygenation of cerebral blood flow. Twenty-six healthy neonates were tested in their cribs while they slept in a silent room. The neonates were exposed to each olfactory stimulus by an experimenter. NIRS monitoring was performed using optodes placed above the bilateral anterior orbito-frontal gyri. The differences in oxygenated haemoglobin (oxy-Hb) values between baseline and stimulation were defined as the change in oxy-Hb. The degrees of change were calculated by an analysis of variance (ANOVA). A 2 (stimulus: breast milk and formula milk) × 2 (probe location: right and left) ANOVA showed that the odour of maternal breast milk (right/left: M = 0.28/0.48) induced a significantly (F = 6.36, p < 0.05) greater increase in the oxygenated blood of the orbito-frontal region than did the odour of formula milk (right/left: M = −0.03/−0.07). Differences in the intensity of odour had no significant influence on the blood oxygenation of the orbito-frontal region. Maternal breast milk odour increased oxygenated blood flow in the orbito-frontal region to a greater extent than did formula milk odour. These results suggest that neonates can distinguish between the odours of maternal breast milk versus formula.     

Breast odour as the only maternal stimulus elicits crawling towards the odour source

In previous studies, newborn infants placed on their mother's chest grasped a nipple and sucked without assistance. Furthermore, neonates sucked preferentially from an untreated breast rather than the alternative breast that had been washed to eliminate its natural odour. This study investigated the influence of breast odours per se on orientated physical movement of neonates. In total, 22 babies were observed during two trials on a warming bed. In one trial, a pad carrying the mother's breast odour was placed 17 cm in front of the baby's nose; in the other trial a clean pad was used. More babies moved towards and reached the breast pad than the clean pad. Conclusion: Natural breast odours unsupported by other maternal stimuli therefore appear to be sufficient to attract and guide neonates to the odour source.     

The olfactory sensitivity of the premature newborn]

This document reviews the main data relating to the structural and functional organisation of olfactory perception in the premature newborn. The chemoreceptive systems (main olfactory, trigeminal, vomeronasal and terminal systems) develop in different chronological orders but quite at very early stage during ontogeny. The premature newborn, despite being immature, has been shown to react to a wide variety of olfactory stimuli. Moreover, the infant seems capable of distinguishing odours of different qualities and intensities, memorising stimuli to which he is regularly exposed to, and categorising different odours based on their hedonic valence. An inventory of the olfactory stimuli to which the infant is regularly exposed to in the incubator is carried out. Several attempts to use pleasant and familiar odours to reduce stress due to separation of the infant from its mother, to promote oral feeding, to make medical procedures more acceptable, and more so, to reduce the respiratory instability of the premature infant, are described. If sustained attention is directed to the olfactory characteristics dwelling inside the incubator, the well-being, health and development of the premature newborn could be improved.     

The biological significance of skin-to-skin contact and maternal odours

Infant-mother bodily contact is believed to be the species-typical pattern of immediate postpartum child care. Mothers and newborns engage in mutually beneficial interactions. Maternal odours stimulate breastfeeding activity and are implicated in individual recognition.

Conclusion: Skin-to-skin contact and exposure to maternal odours facilitate infants' adaptation to the early postnatal environment.     

Mother-infant skin-to-skin contact after delivery results in early recognition of own mother's milk odour

Aim: To determine the effects of mother-infant skin-to-skin contact immediately after birth on infant recognition of their own mother's milk odour and breastfeeding duration until 1 y of age. Methods: Sixty healthy, full-term neonates were randomly assigned to group A with skin-to-skin contact and group B without. One and 4 d after birth, infant responses to the following odour stimuli were observed: own mother's milk, another mother's milk, formula, orange juice and distilled water. Infant facial action was videotaped and the frequency of mouthing movements was evaluated for each stimulus. Nutritional assessment, focused particularly on breastfeeding, was performed every 3 mo on participating infants. Statistical analysis comparing the frequency of mouthing movements with the aforementioned five different odour exposures was performed by ANOVA with Fisher's PLSD. Kaplan-Meier analysis with a log-rank test was used to compare breastfeeding rates between groups. Results: Infants in both groups responded differently to mother's milk odour (either their own or another mother's milk) compared to the other stimuli on days 1 and 4. However, infants in group A demonstrated a larger difference in mouthing movements between their own and another mother's milk odour at 4 d of age (2.6 ± 1.6) compared to infants in group B (0.9 ± 2.0, p = 0.01). Infants in group A were breastfed an average of 1.9 mo longer than the others.

Conclusion: Our study provides evidence that mother-infant skin-to-skin contact for more than 50 min immediately after birth results in enhanced infant recognition of their own mother's milk odour and longer breastfeeding duration.     

Pseudo-maple syrup urine disease due to maternal prenatal ingestion of fenugreek

Fenugreek, maple syrup and the urine of maple syrup urine disease (MSUD) patients all share a characteristic odour originating from a common component, sotolone. Ingestion of fenugreek by mothers during labour resulted in a maple syrup-like odour in their newborn infants, leading to a false suspicion of MSUD.     

Preliminary evidence of a sensitive period for olfactory learning by human newborns

AIM: To test the hypothesis that a brief window of time immediately after delivery may be a particularly sensitive period for olfactory learning by human neonates. METHODS: Fifty-five vaginally delivered newborns were exposed to an odorant for 30 min beginning 4-37 min after birth (Early exposure) or 12-h post-partum (Late exposure). Several days later, newborns' head orientation responses to the exposure odour versus an unfamiliar odour or an odourless control stimulus were tested. RESULTS: Infants in the Early exposure group spent significantly more time oriented towards the familiar scent rather than a novel odour (Z = 2.869; n = 28; p < 0.01), or an odourless stimulus (Z = 2.550; n = 28; p < 0.01). Infants in the Late exposure condition did not respond differentially to the exposure odour versus a novel odour (Z = 1.105; n = 27, p = 0.27), and spent more time oriented towards an odourless stimulus than to the exposure odour (Z = 2.042; n = 27, p < 0.05). CONCLUSION: Infants in the Early exposure group, but not in the Late exposure group, became familiar with the exposure odour and retained a memory trace of it during the test trials.     

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.     

Trimethylaminuria: an under-recognised and socially debilitating metabolic disorder

Primary flavin mono-oxygenase 3 deficiency, an inborn error of choline metabolism, leads to an accumulation of trimethylamine, which because of its associated pungent odour of rotting fish, is a socially crippling disorder. Although it often has its onset in early childhood, it may take years or even decades before the diagnosis is established. In this review the clinical biochemical and genetic features of the disorder are reported. The principles of therapy will also be covered, including dietary, pharmacological approaches, as well as techniques used to manipulate the gastrointestinal environment as a strategy to reduce the gastrointestinal load of trimethylamine.     

Development of the sense of smell, a review

The pre- and postnatal development of human olfaction is described. Data from animal experiments a partially reviewed as a base for understanding of the results of olfactory testing of babies and children. In rat fetuses the vomero-nasal-organ is used as detector of molecules in the amnion fluid. The perinatal aeration of the nasal cavity allows the adequate stimulation of the olfactory epithelium. The early postnatal olfaction is a brainstem function; later the olfactory cortical area are used for the discrimination between odorants. There are only a few investigations about the olfactory function in childhood, so that the testing of olfaction for detecting abnormal brain developments is just in the beginning.     

Neonatal encephalopathy with a pungent body odour

A neonate had transient unexplained bleeding into the gut, severe encephalopathy, and an abnormal pungent body odour. An inherited metabolic defect was excluded. The malodour was due to methanethiol and hydrogen sulphide, identified in urine. These sulphur compounds may have contributed to encephalopathy. Colonic bacteria were the probable source.

     

Attractiveness of amniotic fluid odor: evidence of prenatal olfactory learning?

Human infants are responsive to maternal odors beginning shortly after birth. In several non-human mammals, the fetus is capable of olfactory learning and in some species neonates are attracted to the odor of amniotic fluid (AF). The present study examined the responses of newborn babies to AF in a biologically relevant context, i.e. during their initial attempt to locate the mother's nipple/areola. We observed newborns' spontaneous choice between a breast with the nipple/areola moistened with AF and an untreated breast; 23 of 30 infants chose the AF-treated breast. All babies had been washed before the observations, and only 12/30 sucked their hands/fingers prior to approaching the nipple/areola. In a previous study with unwashed newborns, the corresponding proportion was 27/30 (p < 0.001). We tentatively suggest that the observed attraction to AF odor may reflect fetal exposure to that substance (i.e. prenatal olfactory learning). Because of the salience of biological odors for neonates, products that eliminate or mask such cues should be avoided during the perinatal period.     

Development of olfactory epithelium in the human fetus: Scanning electron microscopic observations

Aims:  Human olfactory epithelium becomes functional at birth, but prenatal development remains unclear. In the present study, we aimed to clarify the development of human olfactory epithelium using scanning electron microscopy (SEM).
Methods:  The development of human olfactory epithelium was observed in 24 externally normal fetuses, which were formalin-fixed and long-preserved, with a crown-rump length (CRL) of 102–336 mm (gestational week 14–38). The olfactory mucosa in the superior wall of the nasal septum near the choana were dissected and observed under SEM. We examined the number of olfactory vesicles per unit area, diameter of olfactory vesicles, and number and length of cilia on olfactory vesicles.
Results:  At circa (ca) CRL 100 mm (ca 14 weeks), olfactory epithelium displayed several olfactory vesicles with 1–2 short cilia per unit area. At ca CRL 150 mm (ca 18 weeks), olfactory vesicles were present in small clusters, and cilia were longer. At CRL lager than 225 mm (ca 26 weeks), olfactory vesicles became located separately from each other, while length and number of cilia per olfactory vesicle were further increased.
Conclusion:  The present findings suggest that fetal olfactory epithelium becomes morphologically almost the same as that in adults in late gestation, much later than previously thought.     

Maternal diet alters the sensory qualities of human milk and the nursling's behavior

Although the majority of human infants are breast-fed for the first few months of life, there is a paucity of information regarding the sensory qualities of human milk and how these qualities are affected by maternal diet. The present study investigated the effects of garlic ingestion by the mother on the odor of her breast milk and the suckling behavior of her infant. Evaluation of the milk samples by a sensory panel revealed garlic ingestion significantly and consistently increased the perceived intensity of the milk odor; this increase in odor intensity was not apparent 1 hour after ingestion, peaked in strength 2 hours after ingestion, and decreased thereafter. That the nursling detected these changes in mother's milk is suggested by the finding that infants were attached to the breast for longer periods of time and sucked more when the milk smelled like garlic. There was a tendency for infants to ingest more milk as well; the lack of a significant effect may be due to the inherent limitations on the total amount of milk available to the infant.     

The effect of olfactory stimulation on energy expenditure in growing preterm infants

Aim: To test the hypothesis that olfactory stimulation in growing healthy preterm infants leads to an increase in resting energy expenditure (REE). Design: A prospective, randomized clinical trial with crossover was conducted in 20 healthy, appropriate weights for gestational age, gavage‐fed preterm infants. Infants were studied while asleep and cared for in a skin servo‐controlled convective incubator. Using a pipette, 15 drops of saturated solution of vanillin (Aldrich, Fallavier, France) were dripped to a cloth diaper that was placed on the opposite side of the incubator. REE was measured by indirect calorimetry (DeltaTrac II, Helsinki, Finland) exactly 1 h after feeding. Each infant was studied twice by randomization: after a period of 20 min of vanillin odour or after 20 min without vanillin odour. Results: We found no statistically significant difference in REE of preterm infants when exposed to vanillin odour (74.5 ± 10.1 kcal/kg/day) in comparison with their REE when not exposed to vanillin odour (79.0 ± 11.3 kcal/kg/day). Conclusions: Vanillin odour does not significantly influence REE in metabolically and thermally stable preterm infants.     

Development of secretory immunity in breast fed and bottle fed infants.

Samples of saliva and nasal secretions were collected sequentially from 15 breast fed and 15 bottle fed infants on five occasions between 6 days and 9 months of age. Total immunoglobulin concentrations of G, M, and A classes, and class specific antibodies to tetanus toxoid and a pool of commensal strains of Escherichia coli were measured by solid phase radioimmunoassay and expressed per milligram of total protein. There were significant differences between feeding groups, which changed with age. Total IgM and IgA concentrations and IgA antibodies to E. coli were higher in the saliva and nasal secretions of breast fed infants at 6 days. There followed a rapid increase in IgM and IgA concentrations in secretions from all infants, and between 6 weeks and 9 months concentrations were higher in the saliva (but not in the nasal secretions) of the bottle fed group. There were no significant differences between the feeding groups for total IgG, specific G, M, and A antibodies to tetanus toxoid, and G and M antibodies to E. coli. These results suggest that breast feeding enhances secretory immunity in the early neonatal period only. By 6 weeks, local antigens are the main source of stimulation for production of immunoglobulin in the respiratory mucosa and thus may be obscuring any additional stimulation by growth factors in breast milk.     

Suckling dysfunction caused by defects in the olfactory system in genetic arhinencephaly mice

Mouse newborns find their mother's nipples and suckle milk by themselves. It has been argued which sense organ they use when locating their mother's nipples to suckle milk. Olfactory or tactile sensory systems are primary candidates. In the present study, we investigated the trigeminal-whisker sensory and olfactory systems in genetic arhinencephaly mouse embryos (Pdn/Pdn). Pdn/Pdn newborns do not suckle milk and die within 1 day after birth. Dysfunction of nipple-searching behavior was clear in Pdn/Pdn newborns. Pdn/Pdn newborns had a complete developmental failure in the olfactory nerve projection to the central nervous system and no olfactory bulb architecture. The trigeminal-whisker system was intact in this strain. From the results of these experiments, it was suggested that the olfactory system is essential for nipple-searching behavior and suckling milk and that the trigeminal-whisker system is not able to substitute for the lack of olfactory input in mouse newborns.     

Expanded endoscopic endonasal resection of an olfactory schwannoma

Olfactory schwannomas are rare tumors of the anterior skull base that are possibly derived from ectopic Schwann cells, perivascular neural tissue, or sensory nerves of the meninges. The authors report the case of a 14-year-old boy with an olfactory schwannoma that extended inferiorly through the cranial base and superiorly into the frontal lobe. Because of the growth characteristics of the tumor and the significant overlying frontal lobe edema, the lesion was approached via an endonasal endoscopic route, as a strategy to minimize brain retraction. This tumor was characterized radiographically as contrast-enhancing with cystic areas and erosion into bone. The tumor showed immunoreactivity for S100 protein and leukocyte antigen 7 (CD57) but not epithelial membrane antigen, supporting the diagnosis of olfactory schwannoma. A gross-total resection was achieved. This approach represents a novel application of endoscopic endonasal surgery to the pediatric neurosurgical context, as well as a favorable outcome in an extremely unusual tumor type, that should be applicable to other appropriately selected pediatric brain tumors.     

Craniofacial Dysmorphia of Frontal Proboscis in Holoprosencephaly

We have examined eleven cases of holoprosencephaly with special emphasis on the frontal proboscis. Although the nostril appears blind ended grossly, the proboscis has a single slender midline nostril lined with squamous mucosa containing numerous sebaceous glands. It is actually connected to a poorly formed but definite nasal cavity microscopically. The inner portion of the nostril tunnel is lined by olfactory mucosa containing numerous subjacent secretary glands. Despite the absence of olfactory bulbs and tracts the cartilaginous nasal capsule is identified along with abnormal nasal cavity. However, the nasal capsule is hypoplastic, and has an aberrant nasal septum and no concha. In severe form of holoprosencephaly, i.e., cyclopia, the nasal capsule is noted above the level of the ethmoid plate, in which case the nasal cavity dose not communicate with nasopharynx because it is too distant from the hypoplastic maxilla. Therefore, choanal atresia is resulted. Although unique maxillary bone comprises the whole upper jaw, the failure of fusion between vomeronasal septum and palatal processes in holoprosencephaly results in abnormal maxillary bone which is characterized by a narrow palate without palatal arch form. Nevertheless, through serial microscopic sections we could find a space between the posterior maxilla and the sphenoid bone, which is composed of adipose tissue and is similar in shape to the nasal capsule. This space is thought to be made for the nasal capsule during early developmental period. The present study suggests that the frontal proboscis in holoprosencephaly is an undescended nose. In most cases it is connected to the aberrant nasal cavity which is located beneath the proboscis. The level of proboscis descends gradually toward normal nose position as the severity of holoprosencephaly decreased from cyclopia, ethmocephaly, cebocephaly, to premaxillary agenesis. Key words: frontal proboscis, holoprosencephaly, craniofacial dysmorphia