New research shows brains of male and female newborns differ

Research led by Trinty PhD student Yumnah Khan has found differences in the brain structure of newborn male and female babies.

The study, the largest investigation of its kind to date, confirms that sex differences in brain structure seen in older children and adults are present at birth.

Yumnah Khan (pictured), of the Autism Research Centre at Cambridge, said:

Because these sex differences are evident so soon after birth, they might in part reflect biological sex differences during prenatal brain development, which then interact with environmental experiences over time to shape further sex differences in the brain.

The study is important because the prevalence of various psychiatric, neurological, and neurodevelopmental conditions differs by biological sex. Researchers are now looking at whether biological factors such as hormones or the placenta contribute to the differences seen in the brains of female and male infants.

A better understanding of these differences, their underlying causes and their onset could help tailor diagnostic and prognostic tools, as well as support strategies to improve health outcomes.

The Cambridge team led by Yumnah analysed the MRI brain scans of 514 newborn babies from the Developing Human Connectome Project. Their findings are published in the journal Biology of Sex Differences.

They found that on average male infants had larger brain volumes than females but when adjusted for total brain volume, female infants had significantly more grey matter and males had significantly more white matter.

Grey matter is responsible for processing and interpreting information, such as sensation, perception, learning, speech, and cognition. White matter comprises long nerve fibres that connect neurons together from different parts of the brain.

With regard to the volume of grey matter in the brains of both sexes, females on average had larger volumes related to memory and emotional regulation, while males on average had larger volumes involved in sensory processing and motor control.

The researchers took into account additional factors, such as birth weight, to ensure the differences they identified are specific to the brain; and they emphasize that the differences between male and female are average differences, with a lot of variation within and overlap between each group.

Trinity Fellow Professor Sir Simon Baron-Cohen, Director of the Autism Research Centre, said:

These differences do not imply the brains of males and females are better or worse. It’s just one example of neurodiversity. This research may be helpful in understanding other kinds of neurodiversity, such as the brain in children who are later diagnosed as autistic, since this is diagnosed more often in males.

The research was funded by Trinity College, Cambridge University Development and Research, the Cambridge Trust, and the Simons Foundation Autism Research Initiative.