Impact of pregnancy on the maternal brain in health and multiple sclerosis

Multiple sclerosis (MS) is a chronic immune-mediated demyelinating disease of the central nervous system characterised by inflammatory lesions and neurodegeneration. Diagnosis often occurs in women of childbearing age, and therefore pregnancy is frequently encountered in women with MS. However, the effect of pregnancy on the MS brain is not well understood, including the impact on inflammatory lesion activity and rate of brain atrophy. Determining the effect of pregnancy on the MS brain is complex due to several confounding factors, including dynamic changes in brain volumes in healthy physiological (non-MS) states and the impact of withdrawing disease-modifying therapies for pregnancy on inflammatory lesion activity. This review first provides an in-depth overview of the profound structural neuroplasticity that occurs during pregnancy in healthy women without neurological disease and its association with maternal caregiving behaviours and maternal-infant attachment measures. These findings are integrated with results of MRI studies in pregnant women with MS to provide a perspective on the multifold influences on brain volume changes in this context. This review also explores the increase in inflammatory lesions observed on postpartum MRI in women with MS, which likely accrue in the postpartum phase mirroring clinical relapse dynamics. Key knowledge gaps are identified, and future research pathways are proposed to improve our understanding of how pregnancy impacts the brain in both healthy and MS states.