Pregnancy alters the size and structure of brain regions involved in understanding the thoughts, feelings, beliefs and intentions of others, according to a study published Monday in the journal Nature Neuroscience.
The changes, thought to have evolved to help a mother focus fully on the needs of her baby, cause some parts of the brain to shrink as neural networks become more specialised.
They last for up to two years after giving birth, researchers found.
However, there was no evidence of any impairment to memory or other mental functions.
The process mirrored the “synaptic pruning” that occurs in adolescent teenagers as their brains mature and rid themselves of excess circuitry.
Twenty-five first-time mothers were studied using magnetic resonance imaging (MRI) brain scans.
The scientists found that during pregnancy the volume of grey matter making up the cell bodies of neurons fell in specific areas of the cerebral cortex, the part of the brain involved in higher functions.
Dr Susanna Carmona co-lead author from the Universitat Autonoma de Barcelona (UAB) in Spain, said: “These areas correspond to a great extent with a network associated with processes involved in social cognition and self-focused processing.”
The same effect was not seen in 20 women who had never been pregnant, or the participants’ male partners.
From the extent of the brain changes, the scientists were able to predict how attached a mother was to her baby after giving birth.
Co-author Dr Oscar Vilarroya, also from UAB, said: “The findings point to an adaptive process related to the benefits of better detecting the needs of the child, such as identifying the newborn’s emotional state.
“Moreover, they provide primary clues regarding the neural basis of motherhood, perinatal mental health and brain plasticity in general.”
Writing in the journal Nature Neuroscience, the researchers said: “On the basis of our results, we may speculate that the female brain undergoes a further maturation or specialisation of the neural network subserving social cognition during pregnancy.
“Very few studies have investigated the effects of pregnancy on measures of social cognition, but there are preliminary indications of facilitated processing of social information in pregnant women, including enhanced emotion and face recognition.”