A new meta-analysis suggests that the odour of maternal milk may have an analgesic action in newborn babies. The findings were published in the journal Breastfeeding Medicine.
Researchers conducted a meta-analysis of 8 randomised controlled trials (RCTs; n=453) identified through a literature search on the PubMed, MEDLINE, CINAHL, EMBASE, Web of Science and the Cochrane databases. The studies compared the effects of maternal milk odour on reduction of procedural pain in babies compared with scentless or other odours.
Babies exposed to maternal milk odour had lower pain scores (standardised mean difference [SMD], −0.81; P<.001) at the time of blood sampling and shorter crying time afterwards (SMD, −8.10; P=.03) compared with those exposed to the scentless group. The heart rate variability and oxygen saturation variability during and after a procedure were significantly lower in maternal milk odour group vs the scentless group and the vanilla group. Also, babies exposed to maternal milk odour had shorter crying duration and lower salivary cortisol levels compared with those exposed to formula milk odour.
According to the authors, when newborn babies are exposed to their favourite milk odour the olfactory information is passed on to the hypothalamus and the hippocampus which mediates the emotional and motivational aspects of odours and subsequently induces physiological and behavioural calming action. They, however, call for further studies of high quality to confirm and quantitate the effect.