Overall, 10-15% of women are diagnosed with postpartum depression (PPD). Though the most significant risk factor for PPD is a history of depression or prior PPD, rates of PPD are as high as 25% among women without prior depression or PPD but with personal risk factors such as reporting little social support or food insecurity during pregnancy and structural factors such as being unmarried. There are profound maternal and pediatric consequences of postpartum mental illness: untreated PPD is associated with maternal morbidity9-11 and impaired child cognitive development. As such, the American College of Obstetricians \& Gynecologists recommends screening all postpartum women for PPD.

There are, however, several structural barriers to the implementation of this recommendation. First, to be screened for PPD, women must attend postpartum visits, and \<60% of women do so. Barriers such as lack of childcare or transportation reduce postpartum visit attendance and disproportionately affect low-income women. Second, pregnancy-related health insurance ends at 60 days postpartum, but PPD can persist for months after delivery, leaving low-income women without subsidized access to screening or treatment. Third, unlike those with known psychiatric illness, many pregnant women without prior mental illness do not receive antenatal mental health screening (unless via universal screening) leading to delayed recognition of and diagnosis of depressive symptoms. Tools to overcome these barriers are sorely needed, particularly for those with the least access who currently fall through the cracks.

Therapy preventing PPD delivered via smartphone applications (apps) may be such a tool. The USPSTF concluded that Cognitive Behavioral Therapy (CBT) - which teaches coping skills to modify maladaptive conditions, behaviors, and physiological responses24, 25 - reduces rates of PPD by 49%. The USPSTF highlighted the Mothers and Babies (MB) CBT program for reducing rates of PPD by 53% among low-income women of color. MB was originally designed as a preventive in-person therapy for low-income English- and Spanish-speaking women without psychiatric illness and contains one parenting education module and multiple CBT modules. MB has started to become a digital health intervention: online MB has been shown to be feasible, and text-message-base MB has been examined in one small study. However, to our knowledge, no studies of app-based MB exist. Online or text-message MB may increase access, but participation with an app would likely be higher for several reasons. Individuals are more likely to have smartphones than internet access: 96% of those aged 18-29 years own smartphones. Additionally, apps provide two advantages compared to other digital health programs: (1) App-based content is accessible without cellular or internet service, (2) Apps serve as just-in-time adaptive interventions,35-37 delivering support tailored to individual behaviors. Thus, app-based MB may decrease PPD while overcoming barriers to care.

Over the last two years, this NIH-funded study has utilized evidence-based user-centered digital intervention design techniques and qualitative research methodology to adapt the MB curriculum into a novel smartphone application, M.Bapp. Similar to MB, M.Bapp contains one parenting education module and multiple CBT-based modules.We now propose a pilot randomized control trial to examine the feasibility, acceptability, and preliminary estimates of effects of the full MB program via M.Bapp (intervention) when compared to app-based digital parenting education (an attention control group). Our long-term goal is to use M.Bapp to prevent PPD among perinatal women at high-risk for the condition due to those with structural or personal risk factors.