How does a TENS unit work during labor?

A transcutaneous electrical nerve stimulation (TENS unit) machine works by sending mild electrical impulses to sticky pads on your back, hips and glutes. These impulses stimulate nerves that run to the spinal cord and block the transmission of pain. They can be used for various types of pain, often back, neck or period pains. They are especially helpful for back labor. A recent study that compared TENS to injectable opioids found that TENS relieved pain just as well as the injectable opioids, but without causing side effects for the mothers and babies. So far, researchers have not reported any bad side effects on mothers or babies from using TENS during labor.

For more information on TENS:

https://evidencebasedbirth.com/transcutaneous-electrical-nerve-stimulation-tens-for-pain-relief-during-labor/