Enlightening pregnancy as a potential pathway to protect maternal circadian functioning and postpartum mood

The perinatal period is characterized by profound psychological, physiological, and behavioral changes that may increase sleep, circadian, and affective disturbances. While sleep disruption across pregnancy and postpartum has been widely documented, far less is known about how this transition shapes circadian health and whether circadian characteristics during pregnancy predict postpartum circadian and affective outcomes. In this study, we characterize circadian preference, circadian phase, circadian function, and light exposure across the transition from late pregnancy to early postpartum, and examine their predictive value for postpartum circadian function and depressive and anxiety symptomatology. Women were followed from the third trimester of pregnancy to 1 month postpartum. At both time points, participants wore a wrist actigraph to derive circadian parameters including the circadian function index (CFI) and circadian phase (L5c), and to quantify mean light exposure. Circadian preference and affective states were also assessed by questionnaires (MEQ, EPDS, STAI-T). Within-subject changes from pregnancy to postpartum were examined, and regression models were used to test whether prenatal circadian and affective measures predicted postpartum circadian function and depressive symptomatology. The transition to postpartum was marked by a significant reduction in CFI and mean light exposure, whereas circadian preference and L5c remained largely stable. During pregnancy, higher CFI was associated with morningness and greater light exposure; however, these associations were no longer evident postpartum. Postpartum CFI was predicted by prenatal CFI and circadian preference, with lower values observed among women with more evening-oriented profiles. In parallel, prenatal affective symptoms showed continuity into the postpartum period, and both prenatal CFI and circadian preference contributed to the prediction of postpartum depressive symptoms. Together, these findings indicate that early postpartum is characterized by a decay in circadian function rather than a shift in circadian phase, identify eveningness as a vulnerability factor during the transition to motherhood, support the use of CFI as an integrative marker of maternal circadian health, and highlight pregnancy as a potential window for circadian-informed interventions aimed at improving postpartum circadian and mood outcomes.