Hi Hun,
I have hired my Mama TENS machine from Boots. Be careful when buying them outright, especially from pharmacies, as most of them are for back pain and are not to be used in pregnancy.
I had a TENS from Boots with my last pregnancy and it was amazing. I didn't have any other pain relief and was amazed at how easy labour was. I think the important thing to remember is as soon as you start getting contractions - start using it straight away.
corrie anne TENS stands for Transcutaneous electrical nerve stimulation. It is a little machine with wires attached with 4 pads on the ends which stick on your back. The machine sends pulses of low-current electricity through the wires. The pulses are so gentle that they're barely noticeable.
The idea is that the electrical pulses will interfere with pain signals that are sent from your back towards your brain. This should relieve pain of labour.
Basically, when you get a contraction, you push the switch on the little machine, beginning at zero and working your way up the more painful the contractions get.
I should also mention that a TENS cannot be used in water for obvious reasons, so it will have to be removed before a water birth.