Medics say the 47-year-old Chinese migrant worker had developed life-threatening blood clots on her brain.
She was travelling from the central Henan province to the southern city of Guangzhou.
But congestion on the train meant the unnamed woman was unable or unwilling to move from her prone position, reports claim.
As soon as she got off the train at Guanzhou station she fainted on the platform.

First Affiliated Hospital of Jinan University in Guangzhou neurologist Meng Heng told local media: "We took out many blood clots, almost two centimetres (just under an inch) in total, which is twice what patients usually have.
"We think she kept the same posture for too long, which compressed the blood vessels on the right side of her neck."
The doctor warned people to avoid staying in the same position for too long, especially when using their mobile phones.




Comment: She never even got up to go the toilet?