Hi!
The only correlation that I know of between miscarriage and LARGE temperature changes is a condition called septic abortion in which the uterus and pregnancy products become infected. An infection can cause a miscarriage or be a consequence of a miscarriage. This condition, like any other bacterial infection can be life threatening if untreated.
There is another syndrome called DIC or disseminated intravascular coagulopathy which causes blood clotting problems and can occur if pregnancy products are retained for longer than 4-5 weeks after the fetal demise. This too can be life threatening.
There is not any relationship that I know of between epilepsy and any of these conditions.
I hope this information is helpful!
Dr B