The ‘gate control’ theory of pain suggests that stimulation of larger peripheral (sensory) nerve fibres inhibits pain signals entering the central pain pathway, reducing the perception of pain; TENS provides this stimulation (Francis 2014). Additionally, it is believed that the electrical stimulation also activates the release of the body’s own endorphins (Bedwell 2011).

TENS is available as a handheld battery-operated unit. Four electrodes (sticky) are placed onto the skin over specific spinal nerves. The electrical output is adjusted according to the frequency (the number per second), duration and amplitude of the pulse (strength of the current), determining how often, how strong and how long the pulses are. Francis (2014) suggests that the conventional use of TENS for labour should have a high rate of pulses with a strong but painless tingling sensation. He is also clear that as the pain of a contraction increases, the TENS intensity should be increased, too, reducing it when uterine muscles relax. Many TENS machines for labour have the facility to boost the intensity in this way.

There are contraindications for the use of TENS. It should be avoided:

It should also be used with caution for women who have epilepsy.

Suitability as a labour analgesic

Studies conflict when considering the effectiveness of TENS, so much so that NICE (2014) state that TENS should not be offered to women in established labour. However, levels of consumer satisfaction are good (Carroll et al 1997) and Francis (2014) suggests that it is the inadequacy and poor quality of the research that causes professionals to doubt TENS, rather than TENS itself. As a non-pharmacological analgesic, it has no known ill effects for the mother (so long as it is used according to the manufacturer’s instructions) or fetus. It allows the woman to mobilize, to utilize other analgesics as well and to have some control – aiding both her physiological and psychological equilibrium. It also offers some distraction. Francis (2014) believes it to be an easy to use, safe and inexpensive non-pharmacological pain reducer. Poole (2007b) suggests that it may take 20–30 minutes for the effects of TENS to be felt.