How pregnancy transforms the brain
Nearly 85% of women experience at least one pregnancy in their lives, and 140 million women become pregnant each year worldwide. The woman’s body profoundly adapts during pregnancy to ensure healthy foetal development. These changes are initiated by a significant increase in oestrogen and progesterone, both hormones impacting the brain. Recent research comparing pre- and post-pregnancy states has shown pronounced modifications in the brain’s neural network. However, brain changes occurring during pregnancy remain largely unknown.
What you need to know
In this study, a healthy 38-year-old woman, pregnant for the first time, underwent 26 magnetic resonance imaging (MRI) scans and blood analyses from 3 weeks before conception to 2 years after birth. Steroid concentrations were measured from blood samples via ultra-sensitive liquid chromatography-mass spectrometry. The analyses were conducted over the entire study period (26 scans) and within the gestational window (19 scans) to explore the relationships between brain modifications, gestational weeks, and steroid hormone levels. Measured brain changes included cortical grey matter volume and thickness, subcortical grey matter volume, and white matter microstructures.
Image analyses consisted of comparisons with a control group of eight non-pregnant participants (including two men), who were scanned 12–50 times over 2–7 months.
What the data revealed
Scan analyses showed reductions in grey matter volume, cortical thinning and an increase in white matter microstructural integrity, which unfolded week by week during pregnancy. These adaptations were closely tied to the rise of steroid hormone levels. Some changes such as reductions in grey matter volume and cortical thickness, persisted two years post-partum, while others appeared transient. For example, the substantial increase in white matter microstructural integrity observed throughout the initial two trimesters of pregnancy returned to baseline by the first scan after birth. The physiological adjustments triggered by the steroid hormones, including water retention, immune function, and sleep patterns, may drive these changes in the brain.
The pronounced grey matter volume differences during pregnancy involved brain regions within sensory, attention, and default mode networks. In contrast, the increased anisotropy in white matter enhanced the communication between emotional and visual processing hubs. These combined changes could be essential for developing maternal behaviour by strengthening the mother’s responses to her baby’s signals.
Not so fast
These findings are limited by the small sample size, as this study involved only one pregnant woman. Consequently, further studies involving a larger cohort of pregnant women are needed to confirm that the observed changes are representative of a broader population.
Some changes can persist two years post-partum suggesting cellular underpinnings and the driving mechanisms remain unknown.
Why does it matter?
This study created the first comprehensive map of the human brain through pregnancy to explore the maternal brain. An increase in the microstructural integrity of white matter during pregnancy was observed for the first time. Globally, brain changes were considerable, some of which were three to four times greater compared with controls scanned over a similar time duration.
In the future, precision imaging of the brain during pregnancy may help detect perinatal depression, affecting one in five women, before symptom onset. It may also facilitate the diagnosis and treatment of neurological diseases, including epilepsy, intracranial hypertension, and multiple sclerosis; disorders that worsen, remit, or co-occur with pregnancy.
Take home messages
1. Reductions in grey matter volume, cortical thinning, and increases in white microstructural integrity have been observed for the first time, and unfold week by week during pregnancy.
2. Some changes, such as reductions in grey matter volume and cortical thickness, persist two years post-partum, while others appear transient.
3. In the future, precision imaging of the brain during pregnancy may help detect and treat several diseases, such as perinatal depression and hypertension.
Guest author: Solène Grosdidier, PharmD, PhD
Reviewer: Barbara Fahmy, MS OTR, MPA
This article was written as part of a series of ‘journal club’ summaries for Scientific Writers Ltd and is based on the following publication.
Title: Neuroanatomical changes observed over the course of a human pregnancy
First Author: Pritschet L, et al.
Journal: Nature Neuroscience
Date online: 16 September 2024
