Acupuncture and acupressure have their origins in Chinese medicine, and are based on the theory that there is a life force energy called qi, which flows from the body's primary organs to the superficial body tissues of the skin, muscles, tendons, bones, and joints, through channels called meridians. Acupuncture/pressure points are mainly found at locations along the meridians.
Most scientific studies have failed to demonstrate the efficacy of acupuncture, however, the easing of labor pain is an exception. Women randomized to acupuncture/pressure or sham have a modest reduction in labor pain, without increasing the risk of C-section. The Sanyinjiao Spleen 6 point, and the Hegu Large Intestine 4 point are most commonly targeted.
TENS has been shown to be no better than placebo for labor pain. Nitrous oxide does provide a modest reduction in labor pain, but would be considered a drug by most people. Aromatherapy has not been shown to affect labor pain.
references:
Barash PG, ed. Clinical Anesthesia. 8th ed. Philadelphia, PA: Wolters Kluwer; 2017: 2854.
https://www.cochrane.org/CD009232/PREG_acupuncture-or-acupressure-relieving-pain-during-labour
http://www.acupuncture.com/education/points/spleen/sp6.htm
