Managing pain during all stages of labor is a key priority for midwives and expectant mommas. This has mainly been addressed with epidural analgesia and opioids in the United States. However, studies have studied an abundance of adverse side-effects to mother and the child for these pain management modalities. The epidural is currently seen as the most effective way to combat labor pain yet it is linked to prolonged labor which can increase potential for complications for either mother or child. Studies have also argued that epidurals increase the incidence of cesarean delivery.
The last thirty years has motivated great interest in alternatives to pharmacologic and anesthesia-based pain management modalities. One of these has been the transcutaneous electrical nerve stimulation machine, or TENS machine, and if not used exclusively, it can also be used in combination with other relief measures inviting no additional risk to either mother or child.
Transcutaneous electrical stimulation (#TENS) for pain control was used in ancient Greece, 63 AD. Guess how? The physician to the Roman Emperor, Claudius, found standing on electrical fish at seaside relieved pain. Aristotle was first to document its use (Bedwell, 2011). In the 16th to 18th century, various electrical devices were used for pain relief, and in the 1970s, the TENs machine was introduced as an option for pain relief in childbirth (McMunn et al., 2009; Njogu et al., 2021).
TENS is reported to work by delivering electrical signals through electrode pads to stimulate the nerves under the skin. These signals act in two ways: they block the transmission of pain signals travelling in nearby nerves, stopping them going through the spinal cord to the brain, otherwise known as the #GateTheory, and they send their own message to the brain, triggering the release of endorphins, the body's own natural pain killer.
The use of TENS in labor has been researched a plethora of times and the evidence is somewhat controversial. Ultimately, it isn't clear what physiological mechanisms are in play when TENS is utilized in labor, and admittedly, while some research studies are supportive, other studies demonstrate that TENS isn't entirely helpful at relieving #pain. There aren't any reports of adverse effects on either mother or child though, and large studies have demonstrated that even when pain relief wasn't significant, mothers report a willingness to use TENS again in future childbearing experiences.
Surveys of midwives have found they feel the TENS is beneficial for women, allowing them mobility, and having the ability to be used with other pain modalities without being invasive. They also appreciated this this modality allowed the woman to be in control and that it had no adverse effects on the unborn child. In England, approximately 1 to 25 percent of all births utilize TENS as a pain relieving modality, although it isn't always recorded in the records so numbers may be a bit higher (McMunn et al, 2009).
Hospitals, more so in England than in the United States may have a borrowing system for utilization of TENS, but most do depend on women to bring in a device previously purchased or rented from a vendor. Insurance often may cover these charges as well. Feel free to schedule a consult if you'd like to discuss options for your labor and #birth. We can even help you understand how to best use the device for discomforts during pregnancy, and in anticipation of labor or even postpartum care.
While a NICE (2007) practice guideline did suggest that TENS not be offered to women, for lack of evidence demonstrating clear pain relief, #midwives acknowledge the need to provide women choices. There are great complexities in managing pain and pain relieving methods contribute to the whole labor experience as a whole, rather than simply freeing the woman of her pain.
The Gate Control Theory
The mechanism of action most supported as to how the TENS offers pain relief is the Gate Control Theory, which has stood the test of time. This theory has been studied for various types of acute and chronic pain for decades, more than fifty years in fact. The Gate Control Theory has been significant because it provided an explanation of how pain was experienced in the body and perceived by the brain.
Interestingly, the thought of how pain was perceived through pain impulses began in ancient Rome, but was not really developed until the 20th century when the central nervous system was better known. This theory proposes that pain comes through gates via afferent fibers to the dorsal horn of the AB medulla. These gates must be open to allow the pain to progress to the brain, but because TENS is believed to act on fibers faster than those which transfer pain, these gates are closed. This is complex though because pain is both psychological and physical, and how the Gate Theory works in that way is still somewhat unclear (Squellati, 2017).
Fear for example can worsen pain for women and closing the gate with positive emotions may decrease pain. Labor pain stems from physiological changes that stimulate the sympathetic system and increase catecholamine, which opens the gates resulting in increased pain. This pain exists to prepare the body for changes necessary for birth.
Later research has demonstrated how emotions such as anxiety or depression can open gates allowing more pain to be perceived and positive emotions can close gates, which decreases pain. Factors that close gates are relaxation and contentment, positive mental factors, physical factors (#massage, transcutaneous electrical nerve stimulation, and #acupuncture), and the right amount of exercise (Squellati, 2017).
The Gate Theory likely works in combination with a release of endogenous opioids by the brain, such as beta-endorphins, which also offer an analgesic effect.
Labor Pain is Universally Known as One of the Most Intense & Painful Experiences
Pain is an unpleasant sensory, subjective, and emotional experience associated with actual or potential tissue damage. Unlike acute and chronic pain situations though, labor pain is associated with a meaningful life experience - the bringing forth of new life.
Labor pain is both visceral and somatic. We experience visceral pain during the early stages of labor and within the second stage, or pushing phase. Nociceptive stimuli from uterine contractions and cervical dilation are transmitted to the posterior nerve root ganglia at T10 through L1. Like other visceral pain types, labor pain refers to the abdominal wall, lumbosacral region, iliac crests, gluteal areas, and thighs (Njogu et al, 2021).
Somatic pain occurs during the transitional and the second stages of labor. These painful impulses result from stretching, distension, ischemia, and injury to the pelvic floor, cervix, vagina, and perineum. These stimuli are conducted via the pudendal nerve through the anterior rami of S2 to S4, and is more sharp and more locally felt (Njogu et al, 2021).
Pain can increase the mother's oxygen consumption, cause nausea, fatigue, respiratory alkalosis, and increased catecholamines, and is even associated with decreased uterine blood flow, poor uterine contractions, decreased cardiac output and increased blood pressure, not to mention increased fear and trauma. Pain relief during labor is essential to reduce its physiological consequences.
The utilization of both high and low-frequency TENS system parameters increases B-endorphins and methionine-enkephalin concentration and the production of inhibitory neurotransmitters such as GABA and serotonin but exhibiting neurotransmitters release (aspartate and glutamate) reduced. These natural analgesics substances inhibit the production of catecholamines (Njogu et al, 2021).
Research Outcomes for TENS
The TENS uses low-voltage electrical impulses to stimulate reas of the lower back primarily where the dorsal horns are located. The TENS may also be used at acupuncture points. Cochrane clinical trials with 1466 women showed the majority of women would want to use TENS again for another labor and did find it helpful. Of course, other researchers argue this finding stating the results are subjective (odd point to argue). Further, the recommendations not to offer the TENS to mothers because some studies do not find them effective, are not doing so because of reasons of safety, but rather because compared to an epidural or opiates, the relief offered with the TENS was quite insignificant. However, this isn't the criteria women use to choose their pain management modality. If TENS offers even a distraction which allows mother to cope with the challenge of labor, and this allows her to avoid the intervention of an epidural or pharmaceuticals, both which can be risky for mom and baby, this may be a huge win for her and a desired outcome. The option should clearly be available to childbearing women along with education on what this modality is likely to offer her.
A randomized control trial in 2016 found women had significantly less pain and waited longer to request pharmacological treatment when the TENS was used for pain management (Santana et al). Several strong randomized control trials have demonstrated a shortened active phase of labor when TENS is utilized (Njogu et al., 2021).
Cold therapy has been used in much the same way, applying a cold pack over the abdomen for five minutes of every fifteen minutes during active labor, and women did feel it decreased pain (Shirvani & Ganji, 2014; Regis et al., 2017). The use of water, either in the shower or birth pool, has also demonstrated ability to reduce pain for the mother in labor (Adams et al., 2013), as have breathing techniques, use of a birth ball (Makvandi et al., 2015), acupuncture (Mafetoni & Shimo, 2016) and massage.
When epidurals and pharmaceutical drugs have the risk of greater admission to the NICU for neonates, even increases in instrumental childbirth which invites their own risks to mom and baby, as well as increased intrapartum fevers and negative impacts on #breastfeeding and TENS has demonstrated no adverse effects to either, then the fact there is any controversy seems somewhat patronizing. It also reflects on the fact that purchasing TENS machines by a birthing facility is somewhat costly (Dias et al., 2022), so if they can make money off of a "more effective" modality such as the epidural, then investing in anesthesia over TENS seems much more "significant."
How do Women use TENS?
Various models of TENS machines are available for use in labor, but also in my own practice, I have often offered these to women who are enduring #miscarriage, discomfort in their lower back during pregnancy or postpartum period (along with a strong recommendation for yoga), but also for #dysmenorrhea (cramping with menses). All are small handheld devices attached to electrode pads, with controls for the woman to operate. TENS devices deliver electrical stimulus through the skin, via electrode pads, in a biphasic pulsed current. Various devices will offer various patterns of pulses, frequently also incorporating a "boost" button. High frequencies modified in time (80-100 Hz) as well as a high pulse width (350 us), seems to offer significant different both clinically and statistically (Baez-Suarez, 2018).
The TENS device allows the woman to control the device both in continuous and boost mode. Some devices do have pre-programmed options to be used at different times in labor. Devices used in labor are frequently dual channel, allowing for two pairs of electrodes to be used simultaneously. These often also allow for the paris of electrodes to be operated independently of each other. The electrodes are large flat pads which are placed on the back bilaterally to the spine at levels T10-L1 and S2-4 (Bedwell, 2011). Other studies have utilized the pads on acupuncture sites however, (Baez-Suarez, 2018), but it appears utilization of the pads within the receptive field for the nerve roots to alter nociceptive transmission in the dorsal horn of the spinal cord results in better outcomes.
TENS itself is experienced as a tingling sensation in the area it is applied, at low doses more like a scratch and when turned up can feel more like a massage. Manufacturers state that pain relief is typical between thirty and sixty minutes, but in my experience, women feel this much sooner. Of course, relief ceases as soon as the device is turned off.
There are recommendations to initiate the TENS as soon as labor is initiated but I am a much bigger fan of ignoring labor at its onset and only offering management strategies as interventions are requested by the laboring woman. Introducing too much too soon invites too much attention to labor, which will prove exhausting, both mentally and physically. Certainly the TENS may be more effective during early labor, but again, if this aspect of labor can be ignored, and mother can continue with her daily activities, my advice is to encourage that until labor stops her to breathe.
More often TENS was utilized in my practice for mothers with more significant lower back pain, often related to persistent posterior fetal positioning. While this wasn't necessary helpful for turning baby into a more optimal position, TENS did help her endure the experience and optimize her pushing efforts because she was less exhausted, and more hopeful.
Few Contraindications for Using TENS
Certainly use in water, such as the shower or birth spa, would be discouraged. Manufacturers also suggest that it not be used by women with pacemakers, cardiac arrhythmia or those suffering from epilepsy. There are some who recommend it not be used prior to the 37th week of pregnancy, and of course, the pads should be used on the back only, not on the abdomen.
References
Adams, J., Frawley, J., Steel, A., Broom, A., & Sibbritt, D. (2015). Use of pharmacological and non-pharmacological labour pain management techniques and their relationship to maternal and infant birth outcomes: Examination of a nationally representative sample of 1835 pregnant women. Midwifery, 31, 458-463.
Baez-Suarez, A., Martin-Castillo, E., Garcia-Andujar, J., Garcia-Hernandez, J. A., Quintana-Montesdeoca, M. R., & Loro-Ferrer, J. F. (2018). Evaluation of different doses of transcutaneous nerve stimulation for pain relief during labour: a randomized controlled trial. Trials, 19(652).
Bedwell, C. (2011). Why do women use TENS equipment and how effective is it? British Journal of Midwifery, 19(6), 348-351.
Blincoe, A. J. (2007). TENS machines and their use in managing labour pain. British Journal of Midwifery, 15(8), 516-519.
Dias, N. T., Santos, P. R., Candido, T. A., de Melo Costa Pinto, R., Magalhaes Resede, A. P., & Pereira-Baldon, V. S. (2022). Effects of the addition of transcutaneous electrical stimulation to non-pharmacological measures in labor pain: Study protocol for a randomized controlled trial. Trials, 23(44).
Makvandi, S., Latifnejad Roudsari, R., Sadeghi, R., & Karimi, L. (2015). Effect of birth ball on labor pain relief: A systematic review and meta-analysis. Journal of Obstetrics & Gynaecology Research, 41(11), 1679-1686.
McMunn, V., Bedwell, C., Nellson, J., Jones, A., Dowswell, T., & Lavender, T. (2009). A national survey of the use of TENS in labour. British Journal of Midwifery, 17(8), 492-495.
Njogu, A., Qin, S., Chen, Y., Hu, L., & Luo, Y. (2021). The effects of transcutaneous electrical nerve stimulation during the first stage of labor: A randomized controlled trial. BMC Pregnancy and Childbirth, 21(164).
Regis, M. M., da Silva Honorio, G. J., dos Santos, K. M., da Luz, S. C. T., Da Luz, C. M., & da Roza, T. (2017). The effect of transcutaneous electrical nerve stimulations (TENS) and cryotherapy in the relief of pain during labor. Manual Therapy, Posturology & Rehabilitation Journal, 15(46).
Santana, L. S., Gallo, R. S., Ferreira, C. J., Duarte, G., Quintana, S. M., & Marcolin, A. C. (2016). Transcutaneous electrical nerve stimulation (TENS) reduces pain and postpones the need for pharmacological analgesia during labour: a randomised trial. Journal of Physiotherapy, 62(1), 29-34.
Shirvani, M. A., & Ganji, A. (2014). The influence of cold pack on labour pain relief and birth outcomes: A randomised controlled trial. Journal of Clinical Nursing, 23(17-18), 2473-2480.
Squellati, R. (2017). Gate theory for labor pain management. International Journal of Childbirth Education, 32(4), 37-41.
Thuvarakan, K., Zimmerman, H., Mikkelsen, M. K., & Gazerani, P. (2020). Transcutaneous electrical nerve stimulation as a pain-relieving approach in labor pain: A systematic review and meta-analysis of randomized controlled trials. Neuromodulation: Technology at the Neural Interface, 23, 732-746.
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