What happens to a mother's brain during pregnancy?

By Tara Chand

Pregnancy is a natural and remarkable process where human life begins and grows. It’s not just about the baby; it’s also an exciting journey for the mother. Along with her body, her brain goes through many changes to support the baby’s development. The increase in hormone levels during pregnancy causes large changes in the brain and body. These changes prepare the mother’s body and mind for parenthood. Previous studies have reported reorganization of the central nervous system due to pregnancy but how exactly these changes happen, especially during the pregnancy phase itself, are largely unknown.

A recent study by Pritschet et al. (2024) provides further insights into these changes by following a healthy 38-year-old woman who became pregnant through IVF (in vitro fertilization). Pritschet and colleagues used magnetic resonance imaging (MRI) scans to track changes in her brain from just before she got pregnant to two years after she gave birth. The study used advanced high-resolution anatomical and diffusion spectrum imaging techniques to look at changes in the gray and white matter of the brain, both in terms of structure sizes and wiring. They also acquired blood samples to look at changes in hormone levels and looked deeper into the hippocampus (a brain region of interest because its size has been linked to hormone levels) during these pregnancy sessions to examine hippocampus subregions at a higher resolution.  

Pritschet and colleagues found there is an increase in hormone levels throughout the pregnancy phase which sharply dropped after childbirth. Both volume and thickness measures of cortical and subcortical areas including gray matter decreased during pregnancy but slightly recovered after childbirth. A similar pattern has been found in CA1, CA2/CA3, and PHC subregions of the hippocampal body. They also found an increase in cerebral spinal flow (CSF), lateral ventricle, and white matter connections throughout the brain during the first and second trimesters of pregnancy. When they looked closely at 400 specific brain regions, they discovered that about 80% showed a decrease in gray matter as pregnancy progressed, which was linked to the rise in pregnancy hormones. Some of these changes lasted up to two years after birth, while others, such as changes in white matter (the brain’s communication pathways), went back to normal after childbirth.

These brain changes might help explain how the mother’s brain adapts to support bonding and parenting behaviors. It also helps researchers to understand individual differences in parental behavior and vulnerability to mental health disorders. While pregnancy is generally a healthy and natural process, some mothers experience depression in the pregnancy phase. Early detection of this depression is difficult, but studies like this can help doctors predict who might be at risk so they can provide early support. 

However, because this study only looked at brain changes in single women during pregnancy, it is challenging to determine if these findings apply to all women. To better understand how pregnancy affects the brain in general, scientists need to study larger groups of women. By doing this, they can create a more accurate picture of how the brain typically changes during pregnancy. 

In summary, this research helps scientists to understand the remarkable changes in the brain as it adapts during pregnancy and highlights how flexible the brain remains in adulthood.

Editor: Yohan Yee

Visuals: Liwen Zhang

Source:

Pritschet, L., Taylor, C.M., Cossio, D. et al. Neuroanatomical changes observed over the course of a human pregnancy. Nat Neurosci (2024). https://doi.org/10.1038/s41593-024-01741-0

Brain Bites Sub-Team
Lead: Alejandra Lopez-Castro; Felipe Rivera