Hi ladies

So I have hired a TENS machine for labour which arrived yesterday. I was just wondering of anyone has used/knows if it safe to use during pregnancy before labour has begun? I have been doing a lot of organising and and cleaning today trying to get ready for bubba's arrival and can now feel my back starting to hurt and stiffen up. Silly me Would be handy to put it on tonight to help with that but I'm just not sure whether I should or not, there is nothing about using it during pregnancy in the instructions I got with it.

Thanks