To build a women's health tracking app, start by defining its purpose and features, such as menstrual cycle tracking, fertility monitoring, symptom management, and exercise logging. Conduct market research to understand user needs and competition. Design a user-friendly interface and implement a secure data collection system. Consider integrating wearable devices for accurate tracking. Use algorithms to provide personalized insights and reminders. Incorporate social features and community support. Test, iterate, and launch the app while ensuring compliance with regulations.