Pregnancy Causes Astonishing Brain Changes – Why haven’t we noticed this before?
by Alexander Bogatch
figures by Salvador Balkus
Have you ever considered pregnancy as a stage of brain development for the mother?
Pregnancy is often described as a period of excitement, anticipation, and extreme change. While the fetus is growing and developing inside of the womb, the mother too is experiencing profound changes. She may notice a faster heartbeat, deeper breathing, a larger burden on the kidneys, and changes in her digestive tract that lead to waves of nausea and discomfort. Many of these physical transformations are due to the hormones estrogen and progesterone, whose release is regulated by the mother’s brain throughout pregnancy. However, despite being released by the brain, we still don’t know if these hormones are affecting the brain itself. In other words, does a mother’s brain also transform during pregnancy?
Tackling this question is a rather immense feat, as the field of neuroscience has largely avoided studying how a woman’s brain changes. In fact, less than 1% of all neuroscience imaging studies completed in the past 30 years focused on women’s health. However, we now have the first clues as to how the brain is altered throughout pregnancy due to a recently published study. For this study, the researchers scanned the brain of a first-time pregnant 38-year-old mother every few weeks throughout the entire course of pregnancy, creating the first dynamic map of the brain during this transformative time. Starting before conception until two years after birth, the mother underwent magnetic resonance imaging (MRI) scans (Figure 1). These scans are obtained by placing the participant inside of a tube-shaped MRI machine, which uses a magnetic field and radio waves to take high quality images of the body’s internal structures. The data from these images revealed fascinating changes in the participant’s brain.
Interestingly, as hormone production ramped up during the gestational period, i.e. the period of time the baby develops in the womb, there was a steady reduction in the mother’s cortical grey matter. The researchers were surprised to see that this reduction in grey matter persisted for two years after the birth of the child, leading researchers to believe this is a long-lasting loss of brain matter.
Reduction in grey matter – should we be scared?
What is grey matter, and should we be scared that pregnant mothers are losing a significant part of it? To understand the implications of these results, let’s dive deeper into why there is grey matter in the brain in the first place. Grey matter, or the wrinkly outer part of the brain, plays an important role in processing information and controlling thoughts, memory, muscle movements, and emotions. The amount of grey matter in the brain is associated with cognitive health, as grey matter volume loss is linked with brain disorders, such as Alzheimer’s disease. However, a reduction in grey matter does not necessarily mean that the mother is suddenly losing brain function. For example, before puberty the brain loses grey matter volume as neural circuits are “fine-tuned,” which has been associated with greater cognitive performance. What the researchers are seeing in pregnancy may be a similar phenomenon, suggesting that the brain is becoming more specialized during this period of time.
Surprisingly, the participant’s grey matter wasn’t the only brain tissue that was experiencing significant changes. The researchers found an opposite transformation happening in the brain’s white matter, which is located deeper in the brain and is important for facilitating communication between different brain regions. Similar to grey matter, brain function is associated with the amount of white matter, and significant decreases in white matter affect cognitive functions, such as attention, memory, and executive function. In the study, the MRI scans showed that in the middle of the gestational period there was a sharp increase in white matter, a change that rebounded back to normal levels at the time of birth. These results are remarkable as there is no prior research to suggest that the brain’s white matter undergoes fluctuations during pregnancy, highlighting the novel insights that can only be gained by creating a dynamic map of the brain (Figure 2).
For now, the explanations for these results are speculative. Looking to the future, the research team hopes to follow up on this study to understand whether these brain changes are representative of a broader population by recording brain changes in more pregnant women. These findings could one day explain how changes in the maternal brain are associated with postpartum depression, a serious mood disorder that affects parents after giving birth.
Why haven’t we noticed this before? A note about gender bias in research
Still, we are only scratching the surface of how the brain transforms throughout pregnancy. Our limited understanding in this field is driven in part by the complexity of studying the human brain, but also from the deep-rooted gender bias in neuroscience research that deprioritizes women’s brain health. The lack of research tackling women’s health has had a large impact on women on a day-to-day basis. For example, women tend to be more misdiagnosed across various neurological conditions, such as Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder. Additionally, certain drugs work better for men than women, and women are about twice as likely to experience side effects of drugs than men (Figure 3).
It is crucial that we talk about gender bias and recognize the importance of studying women’s health, as we may be missing significant changes that are happening in women. Understanding brain changes throughout pregnancy can help us support millions of parents as they navigate this period of time, including treating disorders like postpartum depression. As women’s health research becomes actively prioritized, we will also learn more about neurological conditions that are experienced by people who menstruate, such as the causes behind endometriosis and menstrual migraines. In an article addressing the gender bias in neuroscience research, Dr. Emily Jacobs, the professor who oversaw the pregnancy study, leaves us with this vital insight:
“In all this, we are driven by a radically simple idea: that progress in neuroscience will flourish when the health of people of all genders is valued equally.”
Alexander Bogatch is a PhD candidate in the Biological and Biomedical Sciences Program at Harvard.
Salvador Balkus is a PhD student in Biostatistics at the Harvard T.H. Chan School of Public Health.