Cerebrovascular reactivity in the postpartum period: exploring regional differences using fMRI
Poster No:
2102
Submission Type:
Abstract Submission
Authors:
Joana Pinto1, Sana Suri2,3, Sierra Sparks1, Genevieve Hayes1, Daniel Bulte1
Institutions:
1Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, United Kingdom, 2Department of Psychiatry, University of Oxford, Oxford, United Kingdom, 3Wellcome Centre for Integrative Neuroimaging, Oxford, United Kingdom
First Author:
Joana Pinto, Dr.
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Co-Author(s):
Sana Suri
Department of Psychiatry, University of Oxford|Wellcome Centre for Integrative Neuroimaging
Oxford, United Kingdom|Oxford, United Kingdom
Department of Psychiatry, University of Oxford|Wellcome Centre for Integrative Neuroimaging
Oxford, United Kingdom|Oxford, United Kingdom
Sierra Sparks
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Genevieve Hayes
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Daniel Bulte, Prof.
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford
Oxford, United Kingdom
Introduction:
Women's health has historically received limited attention in medical research. Pregnancy, a pivotal physiological event, triggers widespread adaptations across the body, yet its effects on the brain remain underexplored. While recent findings highlight that pregnancy induces anatomical brain changes persisting up to two years postpartum (Pritschet, 2024), much less is known about accompanying neurovascular changes.
Cerebrovascular reactivity (CVR), an indicator of neurovascular health, reflects the cerebral blood vessel's capacity to regulate blood flow and adjust diameter in response to physiological stimuli, such as changes in blood carbon dioxide (CO2) content (Pinto, 2021). Regional CVR dynamics, described both in terms of amplitude (CVR) and timing (cerebrovascular delay, or CVD), have not been investigated in the context of postpartum changes using MRI. This study seeks to address this gap by comparing CVR and CVD across brain regions between two groups: women who have given birth within the past two years and age-matched women who have never been pregnant.
Cerebrovascular reactivity (CVR), an indicator of neurovascular health, reflects the cerebral blood vessel's capacity to regulate blood flow and adjust diameter in response to physiological stimuli, such as changes in blood carbon dioxide (CO2) content (Pinto, 2021). Regional CVR dynamics, described both in terms of amplitude (CVR) and timing (cerebrovascular delay, or CVD), have not been investigated in the context of postpartum changes using MRI. This study seeks to address this gap by comparing CVR and CVD across brain regions between two groups: women who have given birth within the past two years and age-matched women who have never been pregnant.
Methods:
23 female participants were studied on a 3T Siemens Prisma Scanner at the Wellcome Centre for Integrative Neuroimaging. This group included 13 post-partum women (33.6±4.3 years old, post-partum period up to two years after giving birth) and 10 women with no history of pregnancy (31.0±6.7 years old). Data collected included a high-resolution structural image (MPRAGE, 1mm isotropic, TR/TE = 1900/3.97ms) and a BOLD-fMRI sequence (GE-EPI, 2.4mm isotropic, MB=6, TR/TE=800/30ms) acquired during a gas challenge, whilst expired CO2 values were sampled. The gas challenge was administered using in-house hardware and following a 5% CO2 protocol (Suri, 2021) (Figure 1). All data were analysed using FSL, MATLAB, and R. BOLD-fMRI data were preprocessed using a standard pipeline (motion correction, spatial smoothing 4mm, temporal filtering 100s). The expired CO2 values were processed to retrieve end-tidal values (PETCO2). A bulk PETCO2 time shift was obtained by cross correlating this with the average whole-brain BOLD-fMRI signal. Several PETCO2 traces were created by shifting this bulk-shifted time-course over a range of [-8s to 8s]. GLMs were applied to the pre-processed BOLD-fMRI and the time-shifted PETCO2 traces to obtain two maps: CVR and cerebrovascular delay (CVD), representing the amplitude and time-shift yielding the best fit (i.e., highest amplitude), respectively. CVD corresponds to the delay in the BOLD response to the gas challenge, accounting for differences in lung-to-brain timing and duration of the vasodilation process in each voxel. We tested for differences between the two groups across demographic and physiological features, using t-tests, as well as for brain metrics (CVR and CVD) across nine brain regions using multivariate analysis of variance, adding age as covariate, and post-hoc univariate analysis for each region.
Results:
No significant differences were observed between key demographic and physiological characteristics of the two groups as shown in Figure 1. Figure 2 highlights brain regions where significant CVR (A) and CVD (B) differences are observed between groups.
The postpartum group has greater CVD in the frontal and parietal regions (p=0.01 and 0.03, respectively). The absence of significant differences in CVR amplitude across regions suggests that while the timing of vascular responses is altered, the overall magnitude of cerebrovascular reactivity remains stable across the two groups.
The postpartum group has greater CVD in the frontal and parietal regions (p=0.01 and 0.03, respectively). The absence of significant differences in CVR amplitude across regions suggests that while the timing of vascular responses is altered, the overall magnitude of cerebrovascular reactivity remains stable across the two groups.
Conclusions:
Postpartum women show delayed cerebrovascular reactivity in the frontal and parietal regions compared to women who have never been pregnant. These findings add to growing evidence that the postpartum brain undergoes functional adaptations. Future studies should build upon this pilot study by recruiting larger cohorts and exploring different stages of pregnancy and the postpartum period.
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Anatomy and Functional Systems
Novel Imaging Acquisition Methods:
BOLD fMRI 2
Physiology, Metabolism and Neurotransmission:
Cerebral Metabolism and Hemodynamics 1
Keywords:
Cerebral Blood Flow
Data analysis
FUNCTIONAL MRI
Modeling
MRI
Other - pregnancy; cerebrovascular reactivity
1|2Indicates the priority used for review
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Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
Was this research conducted in the United States?
Were any human subjects research approved by the relevant Institutional Review Board or ethics panel? NOTE: Any human subjects studies without IRB approval will be automatically rejected.
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Provide references using APA citation style.
Pritschet, L. et al. Neuroanatomical changes observed over the course of a human pregnancy. Nat Neurosci (2024).
Suri, S. et al. Study Protocol: The Heart and Brain Study. Front Physiol 12, 364 (2021).
Acknowledgements:
Work supported by EPSRC grant EP/S021507/1, and grants from Wellcome Centre for Integrative Neuroimaging (WIN, University of Oxford) and Alzheimer's Research UK Thames Valley.