Cefar Femina Pregnancy TENS and EMS. TENS is the electrostimulation of nerves in order to reduce pain. Surface electrodes attached to a TENS machine will pass a very low electric current through the skin to the nerves. These nerve endings then send a signal to the brain to block the pain you are feeling, providing you with drug-free pain relief. More recently TENS is being combined with EMS, which is the stimulation of muscles in order to build up strength. And buy this Cefar Femina Pregnancy TENS and EMS Was £169.99 Now £99.00.