Mindfulness is known to decrease psychological distress. Possible benefits in pregnancy have rarely been explored. Our aim was to examine the prospective association of mindfulness with autonomic nervous system function during pregnancy and with later infant social-emotional development. Pregnant women (N = 156) completed self-report mindfulness and emotional distress questionnaires, and had their autonomic function assessed in their first and third trimesters, including heart rate (HR), indices of heart rate variability (HRV), preejection period (PEP), and systolic (SBP) and diastolic blood pressure (DBP). The social-emotional development of 109 infants was assessed at 4 months of age. More mindful pregnant women had less prenatal and postnatal emotional distress (p < .001) and higher cardiac parasympathetic activity: root mean square of successive differences (RMSSD: p = .03) and high-frequency (HF) HRV (p = .02). Between the first and third trimesters, women's overall HR increased (p < .001), and HRV (RMSSD, HF HRV, and low-frequency (LF) HRV: p < .001) and PEP decreased (p < .001). In more mindful mothers, parasympathetic activity decreased less (RMSSD: p = .01; HF HRV: p = .03) and sympathetic activity (inversely related to PEP) increased less (PEP: p = .02) between trimesters. Their offspring displayed less negative social-emotional behavior (p = .03) compared to offspring of less mindful mothers. Mindfulness in pregnancy was associated with ANS changes likely to be adaptive and with better social-emotional offspring development. Interventions to increase mindfulness during pregnancy might improve maternal and offspring health, but randomized trials are needed to demonstrate this.

Major Depressive Disorder (MDD) is one of the most prevalent psychiatric disorders, and involves high relapse rates in which persistent negative thinking and rumination (i.e., perseverative cognition [PC]) play an important role. Positive fantasizing and mindfulness are common evidence-based psychological interventions that have been shown to effectively reduce PC and subsequent depressive relapse. How the interventions cause changes in PC over time, is unknown, but likely differ between the two. Whereas fantasizing may change the valence of thought content, mindfulness may operate through disengaging from automatic thought patterns. Comparing mechanisms of both interventions in a clinical sample and a non-clinical sample can give insight into the effectivity of interventions for different individuals. The current study aims to 1) test whether momentary psychological and psychophysiological indices of PC are differentially affected by positive fantasizing versus mindfulness-based interventions, 2) test whether the mechanisms of change by which fantasizing and mindfulness affect PC differ between remitted MDD versus never-depressed (ND) individuals, and 3) explore potential moderators of the main effects of the two interventions (i.e., what works for whom).