What are the recommendations for using a Transcutaneous Electrical Nerve Stimulation (TENS) unit in a pregnant patient at 30 weeks gestation?

TENS Unit Use at 30 Weeks Gestation

TENS is safe and can be offered to pregnant patients at 30 weeks gestation for pain relief, particularly for musculoskeletal pain, though its effectiveness for labor pain is limited and it should not be expected to provide substantial analgesia during active labor. 1, 2

Safety Profile in Pregnancy

TENS is a non-invasive, non-pharmacological intervention with an excellent safety record throughout pregnancy:

• No adverse events have been reported in any randomized controlled trials examining TENS use during pregnancy and labor 2, 3
• No impact on maternal or fetal outcomes has been documented, including no effects on interventions during labor, delivery outcomes, or neonatal health 2, 3
• The device emits low-voltage electrical impulses that do not pose risks to the developing fetus at any gestational age 1

Clinical Applications at 30 Weeks

For Musculoskeletal Pain (Primary Indication)

TENS is most effective when used for musculoskeletal conditions during pregnancy:

• Back pain, pelvic girdle pain, and other pregnancy-related musculoskeletal discomfort are appropriate indications at 30 weeks gestation 1
• Standard electrode placement over affected areas can be used safely 1
• The patient can control intensity, providing a sense of autonomy 2

For Future Labor Pain (Limited Effectiveness)

If the patient is considering TENS for upcoming labor, set realistic expectations:

• TENS provides minimal pain relief during active labor, with no significant difference in pain ratings compared to placebo in most studies 2, 3
• The Cochrane review found "only limited evidence that TENS reduces pain in labour" 2
• TENS applied to acupuncture points showed better results than back application, with women less likely to report severe pain (RR 0.41,95% CI 0.32-0.55) 2, 3
• Despite limited analgesic effect, most women who use TENS report they would use it again in future labor, suggesting value in perceived control and non-invasiveness 2, 3

Optimal TENS Parameters

When prescribing TENS at 30 weeks, use evidence-based settings:

• High-frequency stimulation (80-100 Hz) with varying frequency over time and pulse width of 350 μs provides the most clinically significant pain reduction 4
• Constant 100 Hz at 100 μs is less effective than variable high-frequency protocols 4
• For back pain: electrodes should be placed parallel to the spinal cord at T10-L1 and S2-S4 levels 4
• Patient-controlled intensity adjustment is essential for comfort and efficacy 1, 2

Practical Recommendations

Offer TENS as an adjunctive therapy for musculoskeletal pain at 30 weeks with the following approach:

1. Explain realistic expectations: TENS is safe but provides modest pain relief, particularly for musculoskeletal conditions 1, 2
2. Recommend high-frequency variable protocols (80-100 Hz, 350 μs) rather than constant frequency for better outcomes 4
3. Ensure proper electrode placement based on pain location, typically paravertebral for back pain 4
4. Encourage patient control of the device to enhance sense of autonomy 2
5. Do not rely on TENS as sole analgesia for labor; it should be considered complementary to other pain management strategies 2, 3

Key Caveats

• TENS does not reduce the need for epidural analgesia or other pharmacological pain relief during labor 2
• The device must have appropriate specifications for obstetric use, including patient-controlled intensity and appropriate frequency ranges 1
• While women report high satisfaction and willingness to use TENS again, this does not correlate with objective pain reduction 2, 3
• TENS used at home in early labor has not been adequately studied, so evidence is limited to hospital-based active labor use 2, 3