摘要:Background: Postpartum anxiety can have adverse effects on the mother and child if left untreated. Time constraints and stigma are common barriers to postpartum treatment. Web-based treatments offer potential flexibility and anonymity. What Am I Worried About (WaWa) is a self-guided treatment based on cognitive-behavioral and mindfulness principles for women experiencing postpartum anxiety. WaWa was developed in Australia and consists of 9 modules with optional weekly telephone support. WaWa was adapted to a Web-based version for use in England (Internet-based What Am I Worried About, iWaWa). Objective: This study aimed to investigate the feasibility (engagement and usability) and acceptability (usefulness, satisfaction, and helpfulness) of iWaWa among English postpartum women with anxiety. Methods: Postpartum (<12 months) women with mild-to-severe anxiety were recruited anonymously via social media during an 8-week period. Participants were randomized to the iWaWa treatment (8 weeks) or wait-list control group. Treatment and study feasibility and acceptability were assessed after the treatment, and anxiety symptoms were assessed at baseline, 8 weeks postrandomization, and 12 weeks postrandomization (treatment group only) using Web-based questionnaires. Semistructured telephone interviews were carried out after the treatment period for a more in-depth exploration of treatment acceptability and feasibility. Results: A total of 89 eligible women were recruited through social media and randomized into the treatment (n=46) or wait-list control group (n=43). Women were predominantly Caucasian, well-educated, married, on maternity leave, first-time mothers and reported moderate levels of anxiety. Dropout rates were high, especially in the treatment group (treatment: 82%, 38/46; wait-list control: 51%, 22/43). A total of 26 women started iWaWa with only 2 women completing all 9 modules. Quantitative and qualitative data suggest iWaWa was experienced as generally useful and helpful. Participants enjoyed iWaWa’s accessibility, anonymity, and weekly reminders, as well as the introduction to the principles of cognitive-behavioral therapy (CBT) and mindfulness. However, iWaWa was also experienced as not user-friendly enough, too long, and not smartphone-friendly. Parts of the content were experienced as not always relevant and appropriate. Participants felt that iWaWa could be improved by having it in a smartphone app format and by making the content more concise and inclusive of different parenting styles. Conclusions: Despite interest in iWaWa, the results suggest that both the study and iWaWa were not feasible in the current format. However, this first trial provides useful evidence about treatment format and content preferences that can inform iWaWa’s future development, as well as research and development of Web-based postpartum anxiety treatments, in general, to optimize adherence.