A new study suggests that the scent of a baby may be the key to helping them deal with the first few months of motherhood. Giving birth rewires the female brain so that the odor of an infant fires up the part which keeps people rational, thoughtful and caring for others.

Researchers from Nagasaki University in Japan performed blindfolded sniff tests with 38 women, half of whom had children. Strips of T-shirts, some worn by four-day-old babies, some by men and others not at all, were repeatedly presented randomly and the participants asked in each case whether they could detect a bodily odor.

At the same time, monitors were tracking activity in the prefrontal cortex (PFC) area of their brains, known as ‘the seat of sober second thought’. When confronted with clothes worn by infants, women with children had an 82 per cent detection rate and underwent significant changes in function in the PFC. Meanwhile, the others had only 68 per cent success and showed virtually no variation in brain activity.

For clothes worn by men, the results were near-identical for both sets of women in detection rate (77 per cent versus 74 per cent) and PFC changes were similar too. The study – published in the journal Chemical Senses – states: “In humans, therefore, it is possible that the female brain is molded when women become mothers.”

This possibility was also supported by a recent neuroimaging study, which reported that the first months of motherhood are accompanied by structural changes in brain regions including the PFC.  “Taken together, our finding suggests that the response of the PFC toward infant odors is changed when women become mothers.”

“This could be important for mothers caring and fulfilling the unique demands of their children. ‘We propose that infant odors enhance mothers’ willingness to approach their infants, which then serves as an intrinsic reward.”

Health psychologist Dr Cynthia McVey, of Glasgow Caledonian University, said: “It’s fascinating that this reaction is being seen in the prefrontal cortex because it’s the part of the brain which governs rational thought.”

Motherhood, especially in the first weeks of a first birth, is extremely stressful and women find it very difficult to deal with the challenges. The smell of an infant works as a natural stimulant to increase the woman’s ability to cope.

This is most effective when the baby is being held close. When, for example, the baby is in distress and crying, which is a situation mothers find extremely hard to deal with at times. It’s also interesting that the women in the study were not new mothers so this effect appears to be long-lasting.

“As a grandmother myself, I cannot explain why the smell on the back of a baby’s neck is so heady – it’s the funniest thing.” Justine Roberts, chief executive of the Mumsnet website, added: “We have always known that, contrary to prevailing opinion, mothers are the embodiment of calm and rational thought so it’s pleasing that the scientists now seem to have confirmed it.”

Last year, Canadian research found that a baby’s scent also raises levels of the pleasure messenger dopamine in the center of the brain. The smell sparks the same reward circuits as eating good food or even having sex.

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