A new study presents the first detailed map of these changes, revealing significant neuroplasticity in adult women. Researchers identified a reduction in gray matter volume and a temporary increase in white matter in the brains of pregnant women. These changes appear to adjust brain circuits to prepare for the demands of motherhood.
During pregnancy, a woman’s body undergoes a number of adaptations to support the development of her baby, including profound changes in the brain, although little is known about how exactly the brain reorganizes itself.
Globally, about 85% of women will become pregnant in their lifetime, with 140 million pregnancies occurring each year. During the 40 weeks of pregnancy, a mother’s body adjusts in several ways: blood volume, oxygen consumption, and metabolism increase, all of which are controlled by hormones such as estrogen and progesterone, which increase up to 1,000-fold.
In addition to regulating these aspects, hormones also affect the central nervous system, leading to the creation of new neurons, the growth of connections between them, and the reorganization of other brain cells.
These changes prepare the mother’s brain for caring for the baby. For example, studies in rodents have shown that certain hormones adjust the brain’s sensitivity to signals from the pups, increasing maternal responsiveness.
In humans, a reduction in the volume of gray matter (the part of the brain responsible for processing information) has been observed after birth, especially in areas linked to empathy and understanding others.
These changes in the brain can last for years, even decades after the baby is born. A recent study found that as early as the third trimester of pregnancy, there is a decrease in the volume of the cerebral cortex, indicating that this is a period of intense brain remodeling.
To better understand these changes, researchers at the University of California, Santa Barbara, conducted a groundbreaking study with a woman who underwent 26 MRI scans during her pregnancy and up to two years after giving birth.
They observed that the volume of gray matter and the thickness of the cerebral cortex decreased as the pregnancy progressed, while sex hormone levels increased. These changes also occur in other areas of the brain, such as the thalamus, hippocampus, and caudate.
However, the decrease in gray matter volume is not necessarily a bad thing. Scientists believe that this may represent a refinement of the brain's circuits, making them more specialized, similar to what happens during adolescence.
Additionally, the researchers identified an increase in the brain’s white matter, which is responsible for connecting different brain regions and facilitating communication between them, which may indicate an important adaptation to the role of the mother.
These findings highlight that pregnancy is a time of complex changes in the brain, but there is still much to be learned about how these transformations occur and their long-term impact.
Although the reduction in gray matter persisted long after delivery, the increase in white matter was temporary. It peaked during the second trimester of pregnancy and returned to pre-pregnancy levels around birth.
A) Standard medical demarcations for pregnancy stages (i.e., trimesters) by week of gestation. B) Steroid hormones increased significantly during pregnancy and declined precipitously postpartum, as is characteristic of the prenatal and postnatal periods. C) A healthy 38-year-old primiparous woman underwent 26 scanning sessions from 3 weeks before conception to 2 years after delivery. D) Summary (i.e., total) brain measurements throughout the experiment. Generalized additive models revealed that GMV, CT, and total brain volume decreased during pregnancy, with a slight recovery postpartum. Global AQ, lateral ventricle, and CSF volumes showed nonlinear increases across gestation, with a notable increase in the second and third trimesters before declining precipitously postpartum. Shaded regions represent 95% confidence bands; solid lines indicate model fit; dashed line indicates delivery. doi.org/10.1038/s41593-024-01741-0
This phenomenon has never been documented with such precision in previous studies using pre- and post-pregnancy scans. According to the researchers, this provides a clearer picture of how dynamic the brain can be in a relatively short period.
“The maternal brain undergoes a concerted transformation during pregnancy, and now we can finally observe this process in action,” said Jacobs, one of the study’s authors.
These changes indicate that the adult brain is capable of undergoing an extended period of neuroplasticity, promoting behavioral adaptations related to parenting.
There are now FDA-approved treatments for postpartum depression, but early detection remains a major challenge. The more we learn about the maternal brain, the better we will be able to provide relief. That is precisely the authors’ goal.
With support from the Ann S. Bowers Women's Brain Health Initiative, led by Jacobs, the team is expanding on these initial findings through the Maternal Brain Project. More women and their partners are being recruited at UC Santa Barbara, UC Irvine, and through an international collaboration with researchers in Spain.
READ MORE:
Neuroanatomical changes observed over the course of a human pregnancy
Laura Pritschet, Caitlin M. Taylor, Daniela Cossio, Joshua Faskowitz, Tyler Santander, Daniel A. Handwerker, Hannah Grotzinger, Evan Layher, Elizabeth R. Chrastil & Emily G. Jacobs
Nature Neuroscience (2024).
Abstract:
Pregnancy is a period of profound hormonal and physiological changes experienced by millions of women annually, yet the neural changes unfolding in the maternal brain throughout gestation are not well studied in humans. Leveraging precision imaging, we mapped neuroanatomical changes in an individual from preconception through 2 years postpartum. Pronounced decreases in gray matter volume and cortical thickness were evident across the brain, standing in contrast to increases in white matter microstructural integrity, ventricle volume, and cerebrospinal fluid, with few regions untouched by the transition to motherhood. This dataset serves as a comprehensive map of the human brain across gestation, providing an open-access resource for the brain imaging community to further explore and understand the maternal brain.
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