(112) باب الشَّهِيدِ
It was narrated that Safwan bin Umayyah said:
"The plague, abdominal illness, drowning and dying in childbirth are martyrdom." (One of the narrators) said: Abu 'Uthman narrated this to us several times, and on one occasion he attributed it to the Prophet.
Reference: Sunan an-Nasa'i 2054
In-book reference: Book 21, Hadith 238
English translation: Vol. 3, Book 21, Hadith 2056