It is narrated from Hazrat Safwan bin Umayyah (may Allah be pleased with him) that dying from the plague, abdominal disease, drowning, or in the state of postnatal bleeding is also martyrdom.
Hadith Referenceمسند احمد / من مسند القبائل / 27642
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف لجهالة عامر بن مالك