The Early Brain Development Projects 

What we want to find out 

The Early Brain Development Projects aim to understand how the brain develops during the earliest stages of life. A key focus of this work is to understand when and how sex differences in the brain begin to emerge. 

Why we’re doing this research

Understanding sex differences in brain development is important because many neurodevelopmental and mental health conditions, such as autism, often affect males and females in different ways and at different rates. We want to understand whether there might be sex differences in early brain development pathways that explain these differences.  

Method

These projects use data from the development Human Connectome Project (dHCP), which contains structural MRI scans from hundreds of infants studied before birth and shortly after birth. This research is divided into three projects: 

  1. Sex differences in human brain structure at birth. This project analysed sex differences in brain volumes in 500+ infants shortly after birth (average age of 8 days). 
  1. Perinatal growth trajectories and sex differences. This project mapped brain growth from prenatal to postnatal development (from 21 weeks’ gestation to one month after birth) in nearly 700 infants. Brain growth pathways were analysed to pinpoint exactly when sex differences first emerge during prenatal development. 
  1. Neonatal brain volumes and behavioural outcomes in toddlerhood. This project investigated whether brain volumes at birth can predict future behavioural outcomes in toddlerhood, such as cognition, language, mental health traits, autistic traits.  

Potential impact


These studies are critical for advancing the scientific understanding of why sex differences exist in various psychiatric and neurodevelopmental conditions. It is possible that males’ and females’ brain development pathways diverge early on, subsequently enhancing the likelihood for males to develop certain conditions and females to develop others, or for the same conditions to present differently in males and females. While the primary aim of these projects is to enhance basic scientific understanding, in the long term and with further research, they may help to contribute to sex-specific diagnostic and support strategies.   

Results

1. Sex differences in human brain structure at birth 

The findings showed that on-average sex differences in brain structure are already present at birth. The most prominent difference was that male infants, on average, had significantly larger brain volumes compared to female infants.  

After accounting for total brain volume, females on average show significantly greater grey matter volumes, while males showed greater white matter volumes.  

Additionally, certain brain regions were relatively larger in females (e.g., corpus callosum, parietal lobe, anterior cingulate gyrus) while others were relatively larger in males (e.g., right medial and inferior temporal gyrus). These findings show that several sex differences previously observed later in development are already present from birth, highlighting the important role of prenatal factors in shaping sex differences in the brain. 

2. Perinatal growth trajectories and sex differences  

This project found that males and females begin to show differences in brain growth trajectories prenatally. The most prominent finding was that males, on average, show faster overall brain growth compared to females. These findings emphasise the prenatal period as a critical window for the emergence of sex differences in the brain. They also provide further support for the hypothesis that prenatal sex hormones play an important role in initiating sex differences in the brain.  

Findings from the “Neonatal brain volumes and behavioural outcomes in toddlerhood” project will be posted here once they are ready – we anticipate this will be by the end of 2026.  

Publications

Khan, Y. T., Tsompanidis, A., Radecki, M. A., Dorfschmidt, L., APEX Consortium, Austin, T., Suckling, J., Allison, C., Lai, M.-C., Bethlehem, R. A. I., & Baron-Cohen, S. (2024). Sex differences in human brain structure at birth. Biology of Sex Differences, 15, Article 81. https://doi.org/10.1186/s13293-024-00657-5  

Khan, Y. T., Tsompanidis, A., Radecki, M. A., Allison, C., Lai, M.-C., Bethlehem, R. A. I., & Baron-Cohen, S. (2026). Mapping brain growth and sex differences across prenatal to postnatal development. Scientific Reports. https://doi.org/10.1038/s41598-025-33981-w  

Funding

Staff

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