Background Excessive gestational weight gain (GWG) is common and associated with negative health outcomes for both mother and child. Mobile health–delivered lifestyle interventions offer the potential to mitigate excessive GWG. The effectiveness of a smartphone app (HealthyMoms) was recently evaluated in a randomized controlled trial. To explore the users’ experiences of using the app, a qualitative study within the HealthyMoms trial was performed. Objective This qualitative study explored participants’ engagement and satisfaction with the 6-month usage of the HealthyMoms app. Methods A total of 19 women (mean age: 31.7, SD 4.4 years; mean BMI: 24.6, SD 3.4 kg/m2; university degree attainment: 13/19, 68%; primiparous: 11/19, 58%) who received the HealthyMoms app in a randomized controlled trial completed semistructured exit interviews. The interviews were audiorecorded and fully transcribed, coded, and analyzed using thematic analysis with an inductive approach. Results Thematic analysis revealed a main theme and 2 subthemes. The main theme, “One could suit many: a multifunctional tool to strengthen women’s health during pregnancy,” and the 2 subthemes, “Factors within and beyond the app influence app engagement” and “Trust, knowledge, and awareness: aspects that can motivate healthy habits,” illustrated that a trustworthy and appreciated health and pregnancy app that is easy to use can inspire a healthy lifestyle during pregnancy. The first subtheme discussed how factors within the app (eg, regular updates and feedback) were perceived to motivate both healthy habits and app engagement. Additionally, factors beyond the app were described to both motivate (eg, interest, motivation, and curiosity) and limit (eg, pregnancy-related complications, lack of time) app engagement. The second subtheme reflected important aspects, such as high trustworthiness of the app, increased knowledge, and awareness from using the app, which motivated participants to improve or maintain healthy habits during pregnancy. Conclusions The HealthyMoms app was considered a valuable and trustworthy tool to mitigate excessive GWG, with useful features and relevant information to initiate and maintain healthy habits during pregnancy. Trial Registration ClinicalTrials.gov NCT03298555; https://clinicaltrials.gov/ct2/show/NCT03298555 International Registered Report Identifier (IRRID) RR2-10.2196/13011

BACKGROUND Excessive gestational weight gain (GWG) is common and associated with negative health outcomes for both mother and child. Mobile health–delivered lifestyle interventions offer the potential to mitigate excessive GWG. The effectiveness of a smartphone app (HealthyMoms) was recently evaluated in a randomized controlled trial. To explore the users’ experiences of using the app, a qualitative study within the HealthyMoms trial was performed. OBJECTIVE This qualitative study explored participants’ engagement and satisfaction with the 6-month usage of the HealthyMoms app. METHODS A total of 19 women (mean age: 31.7, SD 4.4 years; mean BMI: 24.6, SD 3.4 kg/m²; university degree attainment: 13/19, 68%; primiparous: 11/19, 58%) who received the HealthyMoms app in a randomized controlled trial completed semistructured exit interviews. The interviews were audiorecorded and fully transcribed, coded, and analyzed using thematic analysis with an inductive approach. RESULTS Thematic analysis revealed a main theme and 2 subthemes. The main theme, “One could suit many: a multifunctional tool to strengthen women’s health during pregnancy,” and the 2 subthemes, “Factors within and beyond the app influence app engagement” and “Trust, knowledge, and awareness: aspects that can motivate healthy habits,” illustrated that a trustworthy and appreciated health and pregnancy app that is easy to use can inspire a healthy lifestyle during pregnancy. The first subtheme discussed how factors within the app (eg, regular updates and feedback) were perceived to motivate both healthy habits and app engagement. Additionally, factors beyond the app were described to both motivate (eg, interest, motivation, and curiosity) and limit (eg, pregnancy-related complications, lack of time) app engagement. The second subtheme reflected important aspects, such as high trustworthiness of the app, increased knowledge, and awareness from using the app, which motivated participants to improve or maintain healthy habits during pregnancy. CONCLUSIONS The HealthyMoms app was considered a valuable and trustworthy tool to mitigate excessive GWG, with useful features and relevant information to initiate and maintain healthy habits during pregnancy. CLINICALTRIAL ClinicalTrials.gov NCT03298555; https://clinicaltrials.gov/ct2/show/NCT03298555 INTERNATIONAL REGISTERED REPORT RR2-10.2196/13011