Our project aims to develop an innovative low-cost and effective solution to maternal mental health problems in the context of pregnant youth living in adverse conditions in urban areas of a megacity. We plan to develop Motherly, a smartphone app to promote maternal mental health and child development. Motherly app will be visually appealing and provide an engaging user experience with minimalistic layout, enhancing participant engagement. The app will offer a gamified experience ideal for engaging youth in behaviors that can promote mental health, such as stimulating pleasure, productivity, and physical activities, connecting with peers in the geographical area, and eating healthy food. Participants will be awarded points and badges based on behaviors and interactions with other participants. Pregnant youth aged 14-22 living in the Western Region of the city of S_??o Paulo with depression symptoms will participate in a study to test the efficacy of the intervention.