I totally agree with alophysio. Its much better to get a peaceful sleep at night rather than experiment on a foetus. There are so many ways of reducing that pain. Just look for the cause of this pain & undo it. Most often what is needed in the last trimester is just posture care. Interferential is definitely not the best thing that happened to the physio profession for us to risk & harm a foetus, or spend time & money to research it.