The perception of acupuncture as a complementary medical modality (as opposed to an alternative therapy) has grown a lot in the last ten years, as the integration of complementary and conventional medicine continues to take root in the Western world. This is reflected by the surge of scientific studies and increasing evidence that establishes acupuncture as an accepted modality in Western medicine. Approximately 1 million U.S. consumers use acupuncture annually, primarily seeking relief of pain, and acupuncture is now available as a treatment option in most chronic pain clinics.

At present, the research data on acupuncture are mixed. Most trials on the efficacy of acupuncture are equivocal or contradictory. The randomized controlled trials using acupuncture to treat addictions and tinnitus have been predominantly negative. Multiple reviews of identical conditions such as asthma, depression, and bronchitis use overlapping studies and have conflicting interpretations.

However, notable exceptions are randomized controlled trials of acupuncture for emesis, labor pain, and dental pain, which have been overwhelmingly positive. The World Health Organization mentions acupuncture as a nonpharmacologic method to be used in the obstetric population, especially during labor, and emphasizes the necessity of clinical studies to further validate the role of acupuncture. Theoretically, acupuncture is an ideal adjunct for the obstetrics population because it poses a low risk to the mother and fetus and is relatively free of side effects.

The term acupuncture comes from the Latin words acus meaning needle and punctura meaning puncture. It is an ancient science dating back almost 5,000 years. It relies on the stimulation of well-demarcated points situated along set meridians. It is a concept of medicine, which in simple terms suggests that internal homeostasis depends on the unobstructed flow of Qi (chee) through these meridians.

A thorough understanding of surface anatomy is essential to the practice of acupuncture, which involves the placement of fine disposable stainless steel needles at select acupuncture points. There are 365 acupuncture points that lie along 14 meridians, which correspond to organ systems. Acupuncture
needles are inserted at these points and stimulated by various techniques (similarly, acupressure involves holding pressure over the acupoint). These needles range from 1/4 in. to several inches in length and a few thousandths to several thousandths of an inch in diameter. One inch to 1.5 in. is the most commonly used length of needle. Longer needles are used in certain specialized therapies. After needle placement, manual twirling of the needle is performed to elicit a characteristic sensation called De Qi. Other methods used include electrical stimulation, laser, and moxibustion.

The mechanism of action of acupuncture is not completely understood, but it is hypothesized that it involves the rhythmic discharge of nerve fibers that can cause the release of endorphins and oxytocin. One popular theory explaining how acupuncture modulates pain is the neurohumoral hypothesis of acupuncture analgesia. The neurohumoral hypothesis, based on more than 100 scientific papers, states that the pain-relieving properties of acupuncture are partly mediated by a cascade of endorphins and monoamines that are activated by stimulating De Qi, a sensation of numbness and fullness. De Qi is associated with the stimulation of A-delta afferents, which set the cascade in motion. It is interesting that different manners of needle manipulation are known to produce different therapeutic effects.

Although the exact scientific mechanisms remain largely unknown, the analgesia produced by electroacupuncture of different frequencies may be mediated by different endogenous opioids. It is suggested that at lowfrequency (2-Hz) electroacupuncture analgesia is mediated by enkephalin, whereas dynorphins play a role at high-frequency (100-Hz) electroacupuncture analgesia. Among the endorphins, enkephalin and beta-endorphin act at mu and delta receptors. The endomorphins act at the mu receptors alone. Dynorphins are purely kappa receptor agonists. Some studies have suggested that analgesia induced by 2-Hz electroacupuncture is mediated by the m receptor and that of 100-Hz electroacupuncture by k opioid receptors, and that this analgesia is reversible by naloxone. With 2-Hz stimulation electroacupuncture, the release of beta-endorphins into the peripheral blood improves pain, modulates stress, and coordinates contraction of the uterus caused by oxytocin. In animal studies, beta-endorphin levels have been observed to rise in the brain tissue of animals after both acupuncture and exercise. Acupuncture may also decrease sympathetic discharge by the inhibitory effects that the hypothalamic beta-endorphinergic system has on the vasomotor center.

Acupuncture-mediated analgesia is further modulated through neurohumoral pathways. The stimulation of the acupuncture point by needling selectively activates myelinated nerve fibers, and there is neuronal activation at the level of dorsal horn, nucleus raphe magnus in the brainstem, hypothalamus, and thalamus. Subsequently, there is inhibition of the small
unmyelinated pain-carrying fibers. The endorphins also allow for a sense of well-being and relaxation.

In the obstetric population, acupuncture may be used effectively in the treatment of first-trimester nausea and vomiting or hyperemesis, carpal tunnel syndrome, headaches, migraine, backache, sciatica, and other chronic pain syndromes. Acupuncture has also been used to aid in the correction of malpresentation, induction of labor, and pain relief in labor. In the postpartum period, acupuncture has been used to treat postpartum depression and pain from breast engorgement. To date, the evidence about acupuncture for labor analgesia is quite encouraging, and the data available from scientific studies suggests that the analgesic effect is superior to placebo. However, the data are limited, and elegant studies are few.