Infants whose mothers were highly stressed during pregnancy often show altered autonomic nervous system responsiveness to stress after birth. This is important because autonomic responsiveness is associated with childhood behavioral problems. For example, dysregulated  sympathetic reactivity is associated with antisocial behavior, substance use, and anxiety. Mindfulness-based interventions that reduce maternal stress may potentially exert influence on fetal development.

Noroña-Zhou et al. [Psychosomatic Medicine] compared autonomic and behavioral reactivity and regulation in infants whose mothers with elevated stress had previously participated in either a mindfulness-based program or a control group during pregnancy.

The researchers identified 135 6-month-old infants (46% Mixed Race, 36% Black, 17% White) whose mothers had previously completed an 8-week Mindful Moms Training intervention during pregnancy or had served as controls for that study. The mothers were primarily low-income (median income = $18,000) who reported high levels of stress. 

The Mindful Moms program was delivered in eight 2-hour weekly group sessions that combined Mindfulness-Based Stress Reduction, mindful-eating, and support for nutrition and exercise. The control condition was maternity care provided as usual. Previously published results from this trial showed Mindful Moms improved mothers’ levels of stress, depression, activity level, and glucose tolerance relative to controls. 

Sixty-five of the infant-mother pairs were assessed at 6 months of age using a five phase “still face” paradigm to induce infant stress. In this, mothers played normally with their infants for 30 seconds, then stopped interacting with or responding to them and maintained a neutral facial expression for another 30 seconds. The parents then resumed normal responsiveness followed by another “still face” episode and a final resumption of normal responsiveness. 

Infant electrocardiograms (EKGs) were monitored throughout the task. EKG respiratory sinus arrythmias served as a measure of parasympathetic reactivity and the length of EKG pre-ejection periods served as a measure of sympathetic reactivity. Infant behaviors were videotaped and rated by study blinded observers for fussing, withdrawal, and protest as well as visual engagement with objects in the environment.

Results showed infants in the Mindful Moms group increased their sympathetic activity earlier on in the first still face episode than controls, but that controls showed persistent elevated sympathetic activity throughout the remainder of the task whereas mindful infants returned towards baseline.

While all infants showed some decline in positive visual engagement with objects after the first still face episode, mindful infants declined less and showed greater positive visual engagement than controls during the remainder of the task.

There were no group differences in parasympathetic activity or negative behaviors like fussing or withdrawal.

The findings of the study reveal that infants of stressed mothers who participated in a mindfulness intervention show increased sympathetic responsiveness, better sympathetic recovery, and more persistent visual engagement with the environment in response to stress than controls.

The study is limited by its lack of baseline equivalence for gestational age yet this variable was not influential on the treatment effect when covaried statistically. 

Reference:

Noroña-Zhou, A. N., Coccia, M., Epel, E., Vieten, C., Adler, N. E., Laraia, B., Jones-Mason, K., Alkon, A., & Bush, N. R. (2022). The Effects of a Prenatal Mindfulness Intervention on Infant Autonomic and Behavioral Reactivity and Regulation. Psychosomatic Medicine.

Link to study