The natures gate obstetric tens machines come with 4 re-useable electrodes. This means that you can use the tens for pain relief as soon as you start to feel the first twinges of labour. The sooner you apply the tens, the better, as it does take up to 20 minutes for your body to produce its own natural pain killers, endorphins and enkephalines.
If it turns out that you are not in labour, then you can simply remove the electrodes and store them ready for the real thing.
So, yes. Use your TENS machine if you think you are in labour. it does no harm to use in a false start and may be helpful in dealing with the pain of a strong Braxton hicks pain.
WHAT ARE BRAXTON HICKS CONTRACTIONS?
Braxton Hicks contractions are sporadic uterine contractions that start about 6 weeks into your pregnancy, although you won't be able to feel them that early. You probably won't start to notice them until sometime after mid-pregnancy, if you notice them at all. (Some women don't.) They get their name from John Braxton Hicks, an English doctor who first described them in 1872.
How can I tell the difference between Braxton Hicks and true labour contractions?
In the days or weeks before labour, Braxton Hicks contractions may intermittently become rhythmic, relatively close together, and even painful, possibly fooling you into thinking you're in labour. But unlike true labour, during this so-called false labour the contractions don't grow consistently longer, stronger, and closer together.