Healthy mothers showed a clear preference of the own infant's body odor, those with bonding difficulties did not; the degree of odor preference was negatively correlated to bonding difficulties; the ones with bonding difficulties could not identify their own infant's odor

Mother-child bonding is associated with body odor perception. Ilona Croy et al. Physiology & Behavior, https://doi.org/10.1016/j.physbeh.2018.09.014

Highlights
•    Healthy mothers showed a clear preference of the own infant's body odor.
•    Mothers with bonding difficulties did not
•    The degree of odor preference was negatively correlated to bonding difficulties.
•    Mothers with bonding difficulties could not identify their own infant's odor.

Abstract: Mothers can recognize the odor of their baby and typically like this odor very much. In line with this observation, infant body odors activate reward-related brain areas in the mothers. In some mother-child-dyads however, the mutual bond is impaired and mothers have trouble engaging in interaction with their child. We aimed to examine how mothers with bonding difficulties perceive their child's body odor.

In total 75 mothers and their babies (aged 0–12 months) were examined: Twenty-five of those were recruited in a psychosomatic day hospital ward, which is specialized for mother-child bonding disorders. Fifty age-matched healthy women and their babies served as controls. Body odor samples of each baby were collected from bodysuits in a highly standardized procedure. Thereafter, each mother rated the samples of her own and of two stranger's infants in a blindfolded and randomized design. In addition, general olfactory function in terms of threshold and identification ability was tested and the mother reported the bonding to her baby in a standardized questionnaire.

Healthy mothers showed a clear preference of the own compared to odors of strange infant's, while mothers with bonding difficulties did not. Furthermore, the degree of preference was negatively correlated to self-reported bonding difficulties. Mothers with bonding difficulties could not identify their own infant's odor above chance, while control mothers could (p = 0.02). Both groups did not differ in general olfactory function.

We assume that reduced close body contact and interaction time in bonding difficulties may lead to reduced olfactory stimulation and hinder the recognition of the infantile body odor. Within a vicious cycle, a reduced hedonic experience smelling the own baby may prevent women from deliberately approaching the baby. Thus the positive and bond-building consequences of bodily and sensory interaction cannot unfold. As the baby's odor is normally perceived as very pleasant and rewarding, the conscious perception of the infantile body odor may be an additive therapeutic approach for mothers with bonding difficulties.