The "Promoting Healthy Brain Project" (PHBP) aims to improve infant neurodevelopmental trajectories by intervening on the fetal environment. The PHBP will experimentally test whether reducing prenatal maternal stress is associated with improved neurodevelopment in the first year of life. A randomized controlled trial (RCT) of a technology and mindfulness-enhanced prenatal maternal stress-reduction intervention (The Mothers and Babies Course; MB), compared to usual prenatal care. Prospective evaluation of infant neurodevelopmental outcomes will take place through infant age 24 months. Participants assigned to the intervention group will be offered the 12-session MB intervention, a well-studied intervention that will include new mindfulness practice enhancements designed to promote practice of awareness and attention to the present moment. MB visits will be delivered 1-on-1 by a trained facilitator in an open and nonjudgmental way, and will be offered in-person, over the phone, and/or by video chat. Throughout the intervention, all participants (intervention group and control group) will also wear a wireless, "smart" health sensing device (BioStamp Sensor - nPoint Device) that will measure heart rate and motion. Mothers' heart rate variability and self-reported stress and emotion will be monitored using the BioStamp Sensor and brief smartphone surveys. For mothers in the intervention group, patterns of prolonged stress will trigger a "just-in-time adapted intervention" (JITAI) that will be delivered to mothers' smartphones. The booster intervention will include activities that will enhance skills learned in the MB course. All participants will complete self-report measures of prenatal maternal stress, emotion, depression, and skills related to the intervention (e.g., mindfulness). Infant neurodevelopmental health will be measured via brain and behavioral indicators of self-regulation, including performance-based indicators of executive function and corollary prefrontal cortex maturation and dimensional phenotypes of disruptive behavior, particularly irritability.