Hadith 2450
It is narrated from Sayyiduna Safwan bin Umayyah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: “Dying of plague is martyrdom, drowning (to death) is also martyrdom, dying while fighting in battle is martyrdom, dying of abdominal illness is martyrdom, and the death of women in postnatal bleeding is martyrdom.”
Hadith 2451
Sayyiduna Ubada bin Samit (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: "Fighting in the way of Allah is martyrdom, plague is martyrdom, abdominal (disease) is martyrdom, and if a pregnant woman dies because of her fetus, that is martyrdom."