Body’s transformation during and after pregnancy is universally recognized but what about the mothers’ brains? Is the animal instinct something depending on the environment or something ancestral, or does it come from the brain?
A detailed study of a woman’s brain before, during and after pregnancy revealed sweeping neural changes, also months after her baby was born. The results, published September 16 in Nature Neuroscience, is the first comprehensive view of the neural changes that accompany gestation. Every woman knows what to expect for her body during pregnancy, but what to expect when you’re expecting for the brain?
With four MRI scans before pregnancy, fifteen scans during pregnancy and seven scans in the two years after the baby was born, the new study follows the entire arc for one mother.
Researchers’ findings from this precision imaging study show that pregnancy is one the major neuroplasticity moment, characterized by reductions in grey matter volume (GMV), cortical thinning and enhanced white matter microstructural integrity that unfold week by week.
Ok, first point, shrinking brain sounds scary. The brain under scrutiny belongs to cognitive neuroscientist Liz Chrastil, one of the researchers. Over the course of her pregnancy and afterward, Chrastil says she felt fine as her gray matter was reduced and refined, as their neuroscientist colleagues expected. These changes were also tied to the significant rise in steroid hormone concentrations over pregnancy. GMV and cortical thinning persist at 2 years postpartum.
But, point two, the most surprising change of her brain was the white matter tracts, that grew stronger, peaking in the second trimester. These tracts are bundles of information-sending fibers that travel around the brain. The stronger they are, the more efficiently they can carry information. The large increases in white matter microstructural integrity through-out the first and second trimesters of pregnancy fully returned to baseline values by the first postpartum scan, instead GMV and cortical scanning displayed only a modest rebound postpartum.
GMV reduction promotes parenthood
The neuroanatomical changes that unfold during matrescence may have broad implications for understanding individual differences in parental behavior, vulnerability to mental health disorders and patterns of brain aging. Decreases in GMV may reflect ‘fine-tuning’ of the brain by neuro-modulatory hormones in preparation for parenthood.
Human studies have revealed GMV reductions in areas of the brain important for social cognition and the magnitude of these changes corresponds with increased parental attachment. Deeper examination of cellular and systems-level mechanisms will improve our understanding of how pregnancy remodels specific circuits to promote maternal behavior.
Pinpointing the synchrony of gray and white matter changes that unfold in the maternal brain could be key to understanding the behavioral adaptions that emerge during and after pregnancy, such as honing the brain’s visual and auditory responses to infant cues and eliciting maternal behavior.
For both adolescence and matrescence, the consider-able rise in steroid hormone production appears to remodel the brain, promoting a suite of behaviors adaptive to that life stage. How specific neural changes give rise to specific behavioral adaptations has yet to be fully explored with respect to human pregnancy.
A precision imaging approach can help determine whether the pace of pregnancy-induced neuroanatomical changes drives divergent brain health outcomes in women, as may be the case during other rapid periods of brain development. Precision imaging studies could offer clues about an individual’s risk for or resilience to depression before symptom onset, helping clinicians better determine when and how to intervene. Neuroscientists and clinicians also lack tools to facilitate detection and treatment of neurological disorders that co-occur, worsen or remit with pregnancy, such as epilepsy, headaches, multiple sclerosis and intracranial hypertension. Precision mapping of the maternal brain lays the groundwork for a greater understanding of the subtle and sweeping structural, functional, behavioral and clinical changes that unfold across pregnancy.
References:
L. Pritschet et al. Neuroanatomical changes observed over the course of a human pregnancy. Nature Neuroscience. September 16, 2024. doi: 10.1038/s41593-024-01741-0.
