Praise be to Allah.
Al-Bukhari (653) and Muslim (1914) narrated from Abu Hurayrah that the Messenger of Allah (lettings and peace of Allah be upon him) said: “The martyrs are five: the one who dies of the plague, the one who dies of a stomach disease, the one who drowns, the one who is crushed beneath a falling wall, and the martyr who is killed in the cause of Allah, may He be glorified and exalted.”
Ahmad (23804), Abu Dawud (3111) and an-Nasa’i (1846) narrated from Jabir ibn ‘Atik (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “What do you consider to be martyrdom?” They said: Being killed in Allah’s cause. The Messenger of Allah (blessings and peace of Allah be upon him) said: “Martyrdom is seven things besides being killed in Allah’s cause. The one who dies of the plague is a martyr, the one who drowns is a martyr, the one who dies of pleurisy is a martyr, the one who dies of a stomach disease is a martyr, the one who is burned to death is a martyr, the one who dies beneath a collapsed building is a martyr, and the woman who dies because of pregnancy and childbirth is a martyr.” Classed as sahih by al-Albani in Sahih Abi Dawud.
An-Nawawi (may Allah have mercy on him) said:
The scholars said: These types of death are only regarded as martyrdom, by the grace of Allah, may He be exalted, because they are so difficult and painful.
The scholars said: What is meant by the martyrdom of all these people, except for the one who is killed in Allah’s cause, is that in the hereafter they will have the same reward as the martyrs. In this world, however, they should be washed (ghusl) and the funeral prayer should be offered for them.
Please see also the answer to question no 151904 .
And Allah knows best.