Electric blankets are *really* bad. They totally mess with your electric field. Avoid at all costs.
Here's what Dr Mercola says:
Electric blankets create a magnetic field that penetrates about 6-7 inches into the body. Thus it is not surprising that an epidemiological study has linked electric blankets with miscarriages and childhood leukemia.
This pioneering work was performed by Dr. Nancy Wertheimer and Ed Leeper, who originally discovered that magnetic fields were linked to childhood leukemia. Similar health effects have been noted with users of many electric blankets and waterbed heaters will emit EMFs even when turned off.
The devices must be unplugged to delete the EMF exposure Additionally, there is the issue regarding the vibrations that are generated by sleeping on standing water. There is less hard data in this area but some experts are concerned about the consequences.