... But I know pregnancy puts a lot of stress on the heart, since a woman's heart has to pump blood for 2 (in the beginning). Eclampsia is also a thing... Maybe related to that? I can imagine, if there is too much pressure on veins/arteries leading to the legs, blood gets trapped in the lower legs and starts to clot. Then the small clots are dislodged from the legs, travel to the heart where they get stuck, and then stick together to form a bigger clot which blocks off blood flow, causing a heart attack and death. That's all conjecture, though. A place where a bunch of adults get together to talk about cute girls is probably not your authoritative guide to expert medical opinions.