Pregnancy is a period of major physiological change. However, some of these changes (particularly those in the brain) are surprisingly poorly understood. Now, recent research by Laura Pritschet and colleagues, published in Nature Neuroscience, finally sheds new light on this process.

The researchers have generated an unprecedented map of the neuroanatomical changes occurring in the maternal brain from preconception to two years postpartum. Spoiler alert: it’s a lot of changes.

A “heroic” research

The study focused on one 38-year-old woman. She had an MRI scan every few weeks from three weeks preconception and continuing through two years postpartum. Although the sample size is small (just one woman) this type of study (called a longitudinal study) allowed researchers to capture the subtle changes that unfold in the maternal brain throughout pregnancy and after childbirth. The researchers then compared these changes with hormonal levels and typical brain variability to reveal the effects of pregnancy.

As it turns out, gray matter volume and cortical thickness were found to significantly decrease as pregnancy progressed. These reductions do not indicate cognitive decline but rather represent a “fine-tuning” of the brain, particularly in regions associated with social cognition, emotional processing, and maternal behaviors. These changes were tied to the rise in sex hormones such as estradiol and progesterone, which surge during pregnancy.

This adaptation likely enhances the mother’s ability to care for and respond to her newborn, as the brain reorganizes itself to prioritize functions critical for parenting. The long-lasting nature of these changes suggests that pregnancy has enduring effects on the brain, possibly influencing both maternal behavior and mental health for years after childbirth.

The new research sheds so much light on this process that Gina Rippon, one expert in cognitive neuroimaging at Aston University in Birmingham, England, complimented it as “a truly heroic” project, adding: “The data from this study illustrate just how much we have been missing.”

The changes are just dramatic

This study would have likely never been possible without Elizabeth Chrastil, a colleague at the University of California — the volunteer whose brain was scanned. It was intense work, Chrastil says, adding that she didn’t really feel different during the research — even though the changes were significant.

Scientists have known that pregnancy changes the brain, but the scale of the transformation is just dramatic.

While gray matter shrank, white matter integrity improved during pregnancy, enhancing microstructural organization in various brain networks. Basically, the brain seemed to undergo some reorganization. Areas associated with emotional and visual processing (such as the corpus callosum and arcuate fasciculus) displayed increases in white matter integrity throughout pregnancy. These changes likely support the maternal brain’s adaptation to new behaviors required for child-rearing, such as heightened sensitivity to sensory cues from newborns.

Remarkably, some of these changes persisted well into the postpartum period. Decreases in cortical gray matter volume and thickness, for instance, remained noticeable up to two years after childbirth. This long-term neuroplasticity suggests that the maternal brain undergoes enduring adaptations that may be critical for caregiving behaviors.

Interestingly, ventricular expansion and cerebrospinal fluid volume also increased during pregnancy, particularly in the later trimesters, before sharply dropping postpartum. This could indicate increased water retention during pregnancy, a phenomenon often seen in other physiological systems, which could affect the brain’s physical structure. However, the persistence of some brain changes suggests deeper, cellular-level transformations, such as alterations in neuron density or myelination.

Not everything is explained by brain changes

Although the vast majority of areas around the brain experienced changes, some behaviors and emotions associated with pregnancy cannot be explained by brain changes. Furthermore, the study doesn’t tell us how (or if) these changes affect a mother’s health and psychology — nor if all pregnant women experience similar changes.

In fact, the researchers note this is “shockingly” the first study to consistently map brain changes during pregnancy. Out of 50,000 brain imaging articles published in the past 30 years, just around 100 focused on aspects exclusive to women, such as pregnancy.

Thankfully, that’s about to change. This research marks the start of the Maternal Brain Project, an international effort to understand the impact of pregnancy on the material brain. Larger cohorts of both women and their partners are currently being enrolled for studies in the US and Spain.

The study has been published in Nature Neuroscience.