Neural variability across the transition to motherhood: Enhanced moment-to-moment neural variability during mentalizing in first-time mothers.

Pregnancy is known to induce profound structural adaptations in the female brain, especially in regions involved in social cognition. This pre-conception cohort fMRI study examined changes in neural signal variability and functional connectivity during mentalizing tasks among 110 women (Mage = 30.5 years, SD = 3.5, range = 25-41), including 40 first-time mothers, 30 s-time mothers, and 40 nulliparous control women. Participants completed a mentalizing task before and after pregnancy, and, for a subset, 1 year postpartum. First-time mothers exhibited increased neural variability in response to child-related stimuli in the early postpartum period relative to their pre-conception baseline, whereas control women and second-time mothers showed decreases consistent with typical age-related changes. In controls, decreased neural variability correlated with declines in mentalizing task performance, suggesting that neural variability supports flexible and effective cognitive processing. Effects were stimulus- and parity-specific, with first-time mothers showing selective increases to child-related cues and second-time mothers showing distinct changes in adult-related processing. These findings suggest that pregnancy, particularly in first-time mothers, selectively preserves or enhances neural flexibility for processing infant social cues and that neural variability is a key marker of these adaptations.