Pregnancy remodels a mother’s brain

It’s official: “baby brain” is real – but not the forgetfulness to which the term usually refers.

Elseline Hoekzema, Erika Barba-Mueller and a European team found pregnancy remodels a woman’s brain for up to two years – and these changes could boost attachment to her baby.

These brain shifts are the result of the extreme hormonal fluctuations that occur during pregnancy, they write in Nature Communications.

Although we know that less radical hormonal changes — such as those seen during puberty — can modulate human brain structure and function, no one had found if the same happened in a mother’s brain during pregnancy.

To find out, Hoekzema, Barba-Mueller and colleagues scanned the brain of 25 first-time mothers before and after pregnancy, searching for changes in levels of grey matter – the pinkish-grey tissue in the brain involved in information processing.

This group was compared to first-time fathers as well as men and women without children.

The researchers found post-pregnancy changes in the part of the brain related to social processes and cognition among mothers but not fathers, suggesting pregnancy, not a change in lifestyle or activity, was the cause.

They then measured levels of attachment or hostility between mother and child and found that the volume of grey matter lost over pregnancy “predicted quality of mother-to-infant attachment and the absence of hostility toward her newborn”.

These grey matter changes often occurred in the same regions of the brain that lit up when a mother was shown photos of her own baby.

Follow-up sessions showed that new mothers’ grey matter levels didn’t replenish for around two years after pregnancy.

The researchers hypothesised the brain changes are part of an adaptive process to help women transition into motherhood: to encourage mother-baby bonding, to decode social behaviours that could be potentially threatening and to help a mother read emotions expressed by her baby.