Postpartum depression (PPD) affects many urban Nigerian mothers, with inadequate access to timely screening and treatment. A six-week randomized controlled trial was conducted, comparing intervention (mobile app) vs. control groups (standard care). Among 120 participants, 35% of the mobile app group reported improved depressive symptoms compared to 15% in the control group. Mobile health apps showed promise in managing PPD among urban Nigerian mothers. Implementing and scaling up these interventions for broader impact is recommended. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.