Second pregnancy alters women's brain structure and function

A prospective MRI study compared women before and after a first or second pregnancy with nulliparous controls and found widespread decreases in cortical volume, thickness and surface area in both pregnancy groups, with some regional differences between first and second pregnancies and partial persistence of changes into the postpartum period.

Researchers ran a prospective pre-conception cohort study using multimodal 3 T MRI to compare women before pregnancy and in early and late postpartum periods. The study included 30 second-time mothers, 40 first-time mothers and 40 nulliparous control women. It examined cortical volume, thickness and surface area, resting-state networks, white matter tracts and local metabolite concentrations. The aim was to determine whether a second pregnancy produces structural and functional brain changes distinct from a first pregnancy. Key findings: - Both first and second pregnancies were associated with widespread decreases in cortical volume, thickness and surface area compared with control women; median volume decreases in significant regions were about 3.1% for first pregnancies and 2.8% for second pregnancies. - The spatial patterns differed: volume decreases after a first pregnancy were concentrated in the default mode network, while decreases after a second pregnancy were more localized to dorsal/ventral attention and sensorimotor networks. - A multivariate analysis could distinguish first- from second-pregnancy changes in gray matter with about 80% accuracy and could separate pregnant from control women with higher accuracy in the reported models. - Diffusion measures showed changes in white matter: mean diffusivity decreased in the right corticospinal tract after a second pregnancy and fractional anisotropy decreased in the left superior longitudinal fasciculus after a first pregnancy; the right corticospinal tract change was still present in a subset of women one year postpartum. - Magnetic resonance spectroscopy in the precuneus/posterior cingulate region showed a significant increase in total creatine across a second pregnancy in one-sample tests, though group interaction effects did not survive all corrections for multiple testing. Summary: The study reports that pregnancy is associated with measurable structural and functional brain changes and that first and second pregnancies show partly different regional patterns; some changes showed partial reversal but had not returned to pre-pregnancy levels within the observed postpartum period. Undetermined at this time.