I don’t really know the exact reasons why but I’ll list off reasons of what I think
-If her water were to break with the electric blanket on, it could electrocute her and the fetus (undeveloped baby)
-I dont know if this would apply but I’d guess radiation! Which could cause many health problems to not only the pregnant woman but the baby as well!
-sometimes the temperature could get to hot or to cold for the fetus also causing more health problems!
-I’m thinking that sometimes the weight of most electric blankets could apply to much pressure to the stomach which could be bad for the baby
-HOPE THAT HELPEDED! <3