US Midwives' Knowledge and Use of Sterile Water Injections for Labor Pain

Lena Märtensson, CNM, PhD; Maureen McSwiggin, CNM, MS; Judith S. Mercer, CNM, DNSc


J Midwifery Womens Health. 2008;53(2):115-122. 

In This Article


The most interesting result from this survey was that 32% of the respondents use sterile water injections for labor pain. More midwives chose sterile water injections than any other method for managing back pain in labor. More than 75% of the midwives reported very good to moderate pain relief when they used sterile water injections. These data reinforce the literature review which indicates that sterile water injections are an effective pain relief option in labor.[3,10,11,12,13,14,15,16,17,18]

The demographic profile of the respondents was similar to ACNM membership in age and years of experience. The distribution of birth settings in the sample was the same as ACNM members for hospital births, but there were slightly more respondents (9%) practicing in birth centers than among the general membership (6%).[35] A higher percentage of midwives working in birth centers used sterile water injections than midwives practicing in hospitals, although their numbers were too small in this sample for meaningful comparisons. ACNM is not able to retrieve the names of midwives by practice activity or sites, so participants could not be selected for site of practice.

Of the midwives who use sterile water injections, 57% of them stated that they use the intracutaneous technique; 43% use the subcutaneous technique. In a similar survey conducted in Sweden, it was found that 88.1% of the midwives use the intracutaneous technique, 9.8% use the subcutaneous technique, and 2.1% use both injection techniques.[34] Earlier studies have shown that the subcutaneous injections also provide effective pain relief for low back pain during labor[11,15] with less pain during administration.[4] The fact that so many midwives prefer the more painful injection technique may indicate that they are unfamiliar with the literature showing that the less painful subcutaneous injections also are effective. There is no evidence in the literature that more injection pain gives more pain relief.

The amount of sterile water used for injections by the midwives varied. Most guidelines recommend making a wheal on the patient's skin that resembles a purified protein derivative injection for tuberculosis skin test. One midwife stated that she gets longer relief from a larger wheal, although this variation has never been studied.

The majority of the midwives used the recommended four injections, and 75% of the midwives used assistance to administer the injections simultaneously. Midwives who administer the injections alone may do so because of a personal preference or possibly a staffing issue. There was no agreement on whether to administer the injections between contractions or during a contraction. A few of the participants found this issue unimportant. Märtensson[1] recommends simultaneous injections in an attempt to give all injections during one contraction. The idea is that a woman would have less pain from the administration of the injections during a contraction because of the relative high level of pain from the uterine contraction. However, there is no available research on this issue to date.

The results of the survey suggest that there is a lack of knowledge among American midwives about sterile water injections as a pain relief option during labor. One-half of the midwives attending births were not aware of sterile water injections as an option. The most frequent reason for nonuse of sterile water injections was that the midwives had no training or no experience using sterile water injections. The majority of the midwives who stated that they were unaware of sterile water injections as a pain relief method during labor requested to receive information about sterile water injections. These results validate the need for more education regarding sterile water injections as a pain relief option during labor.

Several misconceptions about sterile water injections were evident in the midwives' comments, especially in relation to their conception of efficiency of pain relief. More than one respondent stated that they would not want to inflict the discomfort of the "bee sting" administration if the technique did not work. This negative side effect could be decreased if the injections are administered subcutaneously.[4] Another stated that she would feel as if she was offering her patient a placebo if she used sterile water injections. These misconceptions may be a result of unfamiliarity with the mechanisms of action and the literature ( Table 1 ) on the efficacy of sterile water injections compared to placebo.[10,11,12,15,16,18] Märtensson and Wallin[15] found that women injected with sterile water versus normal saline were more likely to repeat both intracutaneous and subcutaneous injections, most likely because they got better relief because of the effectiveness of the sterile water injections in comparison to a placebo.

A woman's knowledge about pain relieving options or techniques influences the choices she makes with her midwife and affects how her midwife practices. Sterile water injections may not be something that women discuss frequently when talking about their labor experiences or even in childbirth classes. The general public does not have access to this knowledge as readily as providers do. Because of the safety of administration and cost effectiveness, sterile water injections will not be seen as a controversial topic on the evening news. Interestingly, 42% of the midwives estimated that the women they care for were aware of sterile water injection as an option for pain control during labor. This does not mean that these women had accurate knowledge of the physiologic processes that make sterile water injections an efficient provider of pain control. For women who desire to use nonpharmacologic pain relief methods during childbirth, information packets with a concise explanation of these methods and their mechanisms of actions could be a helpful option. The more aware the woman is of the birthing process, including the science behind the pain relieving techniques, the more confident she can be about making informed choices.

An unanticipated finding in this survey was the wide use of hydrotherapy and the rate of epidural use. Interestingly, when the midwives were asked about what techniques they use to manage pain during labor, the estimated percentages of women using traditional epidurals and hydrotherapy were similar.

The survey had several limitations. The sample was limited to active members of the ACNM in 2005 and did not include certified midwives and certified nurse-midwives who were non-ACNM members. The 29% response rate was significantly less than anticipated. Two factors that may have contributed to the low response rate were that reminder cards were not sent out to nonresponders because of time and cost factors, and the time to return the questionnaire was brief. Allowing more time for responses to be returned and sending reminder cards may have increased the questionnaire's rate of return. Another limitation is the potential for bias because of the possibility that midwives who use sterile water injections are more likely to return a questionnaire about this pain relief method than are midwives who do not use it. However, this survey is the first to describe US midwives' knowledge and use of sterile water injections at present and to assess the need for more knowledge about sterile water injections to be disseminated.


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