My personal opinion? I'm not sure I'd turn it off at the powerpoint...I can't reach it even when not pregnant without moving the bed! I used my electric blanket to warm the bed up a lot while pregnant and then turned it off when I got in.

I think electric blankets pose the same 'danger' as hot baths in pregnancy - that is, they're dangerous if you're not being sensible; if you get too warm, turn the blanket off, if the bath is too hot, get out.
So yeah, my personal opinion would be to use an electric blanket if I needed a warm bed, but to do it sensibly, making sure I was hydrated and not going to overheat.