I agree with the above, as long as it is a maternity TENS, ones with "boost" buttons are great for the height of a contraction.
I would say though take care over WHERE you hire from. Last time I ordered a voucher from argos and redeemed it directly on the mamatens website and had no problems.
This time I went to Tensmed ( tensmachine.co.uk ) as they had a deal on, only for them to be totally rubbish on many accounts, no working contact phone number, lots of complaints and poor reviews online, no response to numerous emails sent over a 3 week period, including one requesting my order be cancelled
Even though they advertise 7 week hire they dispatch quite late at 37weeks and state in T&C it can take 4-6 days to arrive. Whereas most companies send it out so you have in time for use at 37w. So if the monitor goes astray in the post/is faulty it doesn't give much time to sort a replacement.
As I was getting a bit worried at this point, I opened a paypal dispute and then escalated it as soon as I realised the phone number given on the paypal account was not only dead, but for a guest house in Bridgend! After paypals investigation, (I don't know what they found) but I got a full refund within a couple of days. Luckily I have since had time to order from somewhere else at increased expense of course.
Basically if their contact address comes up as
OLD TRECASTLE BARN
PENYCLAWDD
MONMOUTH, MONMOUTHSHIRE. NP25 4BW
GB
I would exercise caution, make sure you pay by paypal or other safe method and probably put your due date a little earlier to buy time incase there is a problem I'm sure the 7 week hire period could cover being overdue by miles!
They/he/she do appear to run a few different websites Pregnancytens.co.uk and some sort of dog bed thing? I don't know if they are just a rubbish/poor quality company or actually scammers.