Re: Accidental use of zapper during early pregnancy

Hi Joy,

I found the following relevant information:

Transcutaneous Electrical Nerve Stimulation (TENS)
for musculosketal pain during pregnancy

TENS has been used by pregnant women for many years without any reported side effects for either the
mother or baby. In fact, it has been suggested that TENS enhances placental blood flow (Enzelsberger et
al. 1991). More recently there has been debate about the theoretical risk to the foetus by the electrical field
produced by a TENS unit.
In order to clarify current thinking in this area the ACPWH brought together a panel of experts who reviewed
the literature surrounding this area and together with clinical experience developed these statements. The
expert panel consisted of:-
Yvonne Coldron
Elizabeth Crothers
Jeanette Haslam
William Notcutt
Daphne Sidney
Ros Thomas
Tim Watson

3.0. Consideration of possible areas of risk
When TENS has been used during pregnancy no side effects have been reported in the literature (Walsh,
1997). This is supported by the experience of those on the panel. TENS has been used to increase placental
blood flow (Resnik, 2002), and there were no negative effects. Enzelsberger et al. (1991) suggested that where
TENS was used in pregnancy to increase placental blood flow the peri-natal outcome for women who had
placental insufficiency was improved.

Specific potential areas of concern are the induction of uterine contractions, the effects on the foetal heart
conduction and the possibility of teratogenic effects induced in the foetus. These will be dealt with individually.

3.1. Induction of uterine contractions
There is concern that if TENS is used over specific acupuncture points that uterine contractions may be
stimulated and labour induced. Dunn et al. (1989), tried to induce labour using acupuncture in women who
were post term. The points used were Spleen 6 and Liver 3 points. Although there were methodological flaws
with this paper it was clear that although uterine contractions were stimulated they stopped when acupuncture
stimulation stopped. Smith & Crowther (2004) carried out a Cochrane review as to the efficacy of acupuncture
for the induction of labour. The limited observational studies found that ‘acupuncture for induction of labour
appears safe, has no known teratogenic effects, and may be effective. The evidence regarding the clinical
effectiveness of this technique is limited’. Elden et al. (2005), used acupuncture over contraindicated points (in
particular LI 4) without harm to the mother or foetus.
However, caution should be exercised if using a TENS unit over acupuncture points that could induce labour. If
contractions are induced the stimulation should be stopped. The evidence suggests that then the contractions
would also stop (See section 5.0).
3.2. Induction of changes to foetal development
Where TENS has been used by mothers for treatment of musculoskeletal pain (Walsh,1997) or placental
insufficiency (Enzelsberger et al. 1991; Resnik, 2002) no foetal abnormalities have been reported in the
literature.
3.3. Effects on the electrical conduction within the foetal heart.
The suggested safety precautions when considering any direct effect by application of TENS on the foetus
originate from Bundsen et al. (1982). Since which time there has been no further work in this area. The main
points to consider should be the current density at the skin, the estimated depth of fat under the electrodes
and the position of the baby in utero.
Bundsen et al. (1982), states that when using electrical stimulation for pain relief during labour there are two
safety precautions that should be adhered to.
3.3.1. The current density should not rise above 0.5 microamperes (μA) per square millimetre. (This is worked
out by dividing the output of the unit being used by the surface area of the electrode pad used)
3.3.2. The electrodes should not be placed supra-pubically if the mother is thin i.e., likely to have less than 1
inch of fat and the foetus is occipito-posterior (OP) in presentation. This does imply that if the woman is fatter
and the baby not OP that there is more room for safety. However the placement of electrodes is more
likely to be effective for spinal and pelvic girdle pain when applied posteriorly over the lumbosacral
nerve roots.
If the large 10cm x 5cm electrodes are used and 20 milliamperes (mA) is the average output from any standard
TENS machine, the current at the skin’s surface would be 4 microamperes (μA) per square millimetre.

If the large 10cm x 5cm electrodes are used and 20 milliamperes (mA) is the average output from any standard
TENS machine, the current at the skin’s surface would be 4 microamperes (μA) per square millimetre.
Method of calculation
Assume 10cm X 5 cm electrode with a surface area of 5000mm²
Assume the current at surface is typically 20 mA (this is not an unusual figure when using the TENS unit on the
lumbo sacral spine)
20 mA = 20,000 μA.
Therefore the current density at the skin surface is
20,000/5000 μA per mm² = 4 μA per mm²
It is most likely that the current density at the skin will be considerably less by the time that it
reaches the uterus due to dispersal within conducting tissues.

4.0. The balancing of potential risks against the use of strong medication.
We cannot find any reports that suggest negative effects have been produced when TENS has been used
during pregnancy. However, in clinical practice TENS is not the first treatment of choice for a women
presenting with musculoskeletal pain during pregnancy. Initial treatment should be aimed at correcting any
joint or muscle dysfunction and devising a rehabilitation programme. However, if pain remains a significant
factor then TENS or acupuncture would be preferable to the use of strong medication that could cross the
placental barrier and affect the foetus. The risk from intervention with strong medication during the first
trimester is slightly higher than in the later stages of pregnancy and therefore TENS as a method of pain relief
during the first trimester should be more carefully considered. However, as stated previously no negative
effects have been reported following from the use of TENS during any of the stages of pregnancy. TENS
presents with lower risk than strong medication for the relief of pain and is therefore preferable.

5.0. Clinical Application, Cautions and Pre-cautions.
Although this statement declares that TENS is of lower risk to the foetus than strong medication careful
consideration of the appropriate use of TENS must be given. When applying TENS to the pregnant woman;
• the usual contraindications and precautions should be observed
• extra caution should be taken if the woman has epilepsy or has a very irritable uterus or has had a
history of early miscarriage or abortion. In these situations the patient should be fully informed and
in conjunction with the appropriate medical practitioner a clinical judgement should be made so that
consent to the TENS treatment can be given or withheld
• the current density should be kept low. If the large 10 x 5 cm electrodes are used with a standard TENS
machine this should not be a problem
• caution should be taken when placing TENS electrodes over acupuncture points that are considered to
be the most likely to induce labour. Grant & Ma (2004) suggest that the points that should be considered
with care for use during pregnancy are; LI-4 (dorsal aspect thumb web*); SP-6; BL60 and BL67 (all around
the lower half of the leg and ankle*). West (2000) also includes GB21 (middle fibre of trapezius*) which is
used very commonly for shoulder pain. However in a retrospective study by Ternov et al. (2001), of 167
consecutive women who had acupuncture for low back pain in pregnancy and using LI-4; ST36 (around
the head of fibula*); GB34 (around the head of fibula*); BL-60 (ankle*); GV20 (top of head*) and other
tender points on the back only one potentially serious side effect was observed. With this patient the risk
of side effects from acupuncture were low compared to the side effects of medication. This author seems
to have used a large number of the contraindicated points with no serious side effects. We also know
from Dunn et al. (1989), that should uterine contractions be stimulated that they will stop if the machine is
turned off
Before using acupuncture or TENS on acupuncture points when the patient is pregnant the therapist should
make sure that he/she is fully compliant with Rule 1 of the CSP Standards of Practice.
* These are general descriptions of the areas involved so that those not versed in acupuncture can be aware
of the areas that are under discussion. For more accurate descriptions of these points consultation of an
acupuncture text is recommended.
• in the rare circumstances where a patient has an implant such as a pacemaker or defibrillator then the
use of TENS should be considered and monitored by a specialist Pain clinic or Cardiology clinic. It is
not impossible for patients to use a TENS unit and be fitted with an implant of this type but there is
substantial risk of interference and this is out of the physiotherapist’s realm. There would need to be a
team approach to the treatment, needs of a patient with implanted stimulators. Sometimes the implants
may be neurogenic stimulators and any prospective use of TENS should not be tried until discussions
with the appropriate consultant/s have taken place. In any case where a patient has implanted stimulators,
the first time TENS is tested it should be in an acute setting where resuscitation facilities are available.

ACPWH guidance on the safe use of
Transcutaneous Electrical Nerve Stimulation (TENS)
for musculosketal pain during pregnancy

From: http://www.electrotherapy.org/downloads/Modalities/TENS%20in%20pregnancy%20gu...

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The zapper is similar in many ways to a very mild TENS unit and the same information should be able to be applied.

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