Acupuncture for the Management of Postpartum Uterine Contraction Pain Following Vaginal Delivery: A Protocol for a Randomized, Sham-Controlled Trial

Introduction

Uterine contraction pain (UCP) following vaginal delivery is a paroxysmal, severe visceral cramping pain that occurs during the course of uterine involution and physiological hemostasis in the early puerperium.^1,2 Forty-seven percent of women experience significant UCP within 48 hours postpartum, and this pain exhibits significant variation by parity.² Due to decreased uterine muscle tone, multiparous women often require stronger intermittent contractions to clear accumulated blood from the uterine cavity, thereby experiencing more intense cramping pain compared to primiparas. This distressing visceral discomfort frequently impairs maternal sleep quality, emotional well-being, and postpartum physical recovery.^3,4

Managing UCP after vaginal delivery presents unique challenges. Routine administration of exogenous oxytocin is a standard clinical practice to prevent postpartum hemorrhage, while endogenous oxytocin released during breastfeeding is crucial for facilitating physiological uterine hemostasis.^5,6 Both can markedly increase the frequency and intensity of uterine contractions. However, pharmacological pain relief options are limited due to safety concerns and potential adverse effects during lactation. Although the American College of Obstetricians and Gynecologists (ACOG) recommends the use of non-steroidal anti-inflammatory drugs (NSAIDs),⁷ their use is somewhat limited due to the risk of the drugs entering breast milk and potential gastrointestinal adverse events.⁸ Therefore, there is an urgent need for effective non-pharmacological interventions to alleviate UCP.

Acupuncture, as a traditional non-pharmacological therapy, has been widely validated for its analgesic effects in visceral pain management.^9,10 Its mechanisms are believed to involve the regulation of the endogenous opioid system and improvement of pelvic microcirculation, which may help alleviate the ischemic state of the contracting uterus.^11,12 Clinical studies have shown that acupuncture can effectively relieve symptoms of UCP during the postpartum period, reduce the frequency of episodes, and shorten the duration and days of pain.^13–15 Although these studies suggest that acupuncture has advantages over control groups in treating postpartum UCP, none of them used a sham/placebo acupuncture control and implemented blinding. Consequently, placebo effects cannot be excluded, and the quality of evidence remains limited. Furthermore, none of these studies observed the entire course of postpartum UCP, nor did they assess the two factors closely related to this pain: vaginal blood loss and lactation volume.

To address these gaps, this trial is the first to use a non-penetrating blunt needle via the Park Sham Device (PSD) as a placebo control with blinding of participants, outcome assessors, and data analysts, and the first sham-controlled trial to comprehensively evaluate pain course, vaginal bleeding, lactation, and maternal psychological status. To account for differences in pain perception between primiparous and multiparous women, we used strict stratification by parity. This study primarily aimed to compare the analgesic efficacy of verum acupuncture (VA) versus sham acupuncture (SA) for UCP on postpartum day 3. Secondary endpoints included UCP levels at days 1, 2, 10, and 17, pain characteristics, vaginal bleeding, lactation output, psychological status, and treatment safety. Accordingly, this study protocol is designed to generate high-quality evidence supporting acupuncture as a safe and effective intervention for the management of postpartum UCP.

Materials and Methods

Study Design

Designed as a prospective, randomized controlled trial with blinding of participants, outcome assessors, and data analysts, this study is scheduled to be conducted at the Ludian County Hospital of Traditional Chinese Medicine. The protocol has received ethical approval from the Medical Ethics Committee and is publicly registered with the Chinese Clinical Trial Registry (identifier: ChiCTR2400086059). Adherence to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) checklist is strictly maintained (as seen in Supplementary material 1).¹⁶ Figure 1 illustrates the study flowchart, while Table 1 outlines the schedule of events.

Table 1 Proposed Timeline for Participant Recruitment, Treatment Protocol, and Data Collection

Figure 1 Flow diagram.

Participants

Recruitment Procedures

Participants’ identification relies primarily on recruitment notices positioned throughout the Obstetrics Inpatient Department at the Ludian County Hospital of Traditional Chinese Medicine. To ensure rigorous adherence to eligibility standards, the screening responsibility is exclusively assigned to attending obstetricians possessing a minimum of five years of clinical practice and standardized training. Following strict verification of inclusion and exclusion criteria, eligible individuals receive a comprehensive briefing regarding the study’s rationale, procedural details, potential risks, and benefits. Written informed consent is obtained only after participants fully comprehend their rights, including the unconditional option to withdraw at any stage.

Eligibility Criteria

Eligibility for enrollment is limited to women aged 18 years or older who have delivered a single live neonate vaginally following a term pregnancy (37 to 42 weeks of gestation). Furthermore, candidates must demonstrate an intent to breastfeed, be able to actively cooperate, and provide written informed consent.

Potential participants were excluded if their labor required instrumental intervention, specifically vacuum extraction or forceps delivery. We also disqualified individuals presenting with severe pregnancy-related or puerperal complications, as well as those with pre-existing pelvic pathologies such as adenomyosis or pelvic inflammatory disease. In terms of general health, exclusion applied to patients with significant central nervous system disorders (eg, epilepsy), rheumatic immune diseases, coagulation defects, or psychiatric conditions (eg, schizophrenia, mania) that impair communication and comprehension. Furthermore, the study barred participation for those with a history of chronic analgesic dependency, concurrent enrollment in other clinical trials, or specific contraindications to the interventions—including hypersensitivity to acupuncture or NSAIDs, local skin lesions at needling sites, and active gastrointestinal conditions like peptic ulcers or bleeding.

Randomization and Blinding

Eligible participants were randomly assigned in a 1:1 ratio to either the VA group or the SA group, stratified by parity (primiparous vs. multiparous). The randomization sequence was generated using IBM SPSS Statistics 28.0 software (IBM Corp., Armonk, NY, USA). To ensure allocation concealment, an independent research assistant not involved in the recruitment or treatment process prepared the group assignments in sequentially numbered, opaque, sealed envelopes. These envelopes were opened strictly in sequence only after the participant’s baseline eligibility had been confirmed. This study was designed with blinding of participants, outcome assessors, and data analysts, all of whom remained unaware of the specific group allocation throughout the trial. Acupuncturists were unblinded. To maintain blinding in the SA group, a non‑penetrating blunt needle delivered via the PSD was used. The device looks identical to the verum needle, but the blunt tip only creates a pricking sensation on the skin surface without penetrating it. The success of the blinding procedure was assessed within 24 hours after the final treatment session by asking participants to guess their group assignment. Emergency unblinding was permitted only when knowledge of the treatment assignment was essential for the medical management of a participant, such as in the event of a Severe Adverse Event (SAE). In such cases, the principal investigator had to authorize the code breaking, and the details had to be documented in the Case Report Form (CRF). If unblinding occurred, the participant was withdrawn from the intervention but retained for safety analysis, while the blinding of other participants and study personnel remained intact.

Sample Size

The sample size was determined using PASS 2021 software (NCSS, LLC, Kaysville, UT, USA) based on a superiority trial design to evaluate the analgesic efficacy of VA compared to SA. We hypothesized that the VA group would demonstrate superior pain relief with a minimum clinically important difference of 1.6 cm on the Visual Analog Scale (VAS), which was established as the superiority margin.¹⁷ Drawing from previous research, we anticipated a true mean difference of 2.0 cm in VAS reduction between the two groups.¹⁸ The standard deviation for both groups was assumed to be 1. Using a one-sided significance level of 0.025, a statistical power of 80%, and a 1:1 allocation ratio, the calculation indicated that 100 participants per group. To account for a potential dropout rate of 15%, the final sample size was adjusted to enroll 118 participants per group, resulting in a total of 236 participants. A preliminary investigation indicated that multiparous women accounted for 83.9% of the target population, while primiparous women accounted for 16.1%. Based on these proportions, we estimate that each group will consist of approximately 99 multiparous women and 19 primiparous women.

Interventions

Routine postpartum care and oxytocin administration were provided to all participants, with no additional analgesics permitted. Acupuncture was administered starting on the day of vaginal delivery, twice daily for three consecutive days, with needles retained for 30 minutes per session. Participants reporting unbearable pain during the observation period could receive rescue analgesia in the form of Diclofenac Sodium suppositories (50 mg; Hubei Tungshun Medicine Co., Ltd). Any administration of rescue medication, including the exact dosage and post-treatment pain assessment, was strictly documented in the CRF. Acupuncture interventions targeted four bilateral acupoints (ST36, LR3, SP8, and GB41), for a total of eight needling sites (Figure 2), localized in accordance with the Chinese national standard GB/T 12346–2021. ST36 and LR3 are recognized as core acupoints for analgesic effects in various pain conditions.¹⁹ Together with SP8, they alleviate visceral pain (eg, dysmenorrhea) by tonifying and regulating qi and blood. GB41 acts on the Dai meridian, which encircles the waist and can indirectly regulate the uterus. The study employed PSD (Suzhou Medical Supplies Factory, China), which consisted of a guide tube (4×20 mm) and opaque bases. Acupuncture needles: Disposable sterile needles (0.30×40 mm, ‘Huatuo’ brand). Placebo needles: Blunt-tipped stainless steel needles (0.30×40 mm) identical in appearance to the verum needles.

Figure 2 Acupoints selected in this study.

VA Group

Licensed acupuncturists administered the intervention using sterile single-use needles (0.30 × 40 mm) combined with the PSD. Following standard skin disinfection with 75% ethanol, the PSD was adhered to the skin at the selected acupoints. The needle was then tapped through the device to penetrate the skin. All needles were inserted simultaneously, with insertion depth standardized to 10–15 mm for ST36 and SP8, and 5–10 mm for LR3 and GB41. Manual stimulation techniques, including lifting, thrusting, and twirling, were applied to elicit the characteristic deqi sensation (eg, soreness, numbness, or distension). Local warmth was maintained at the acupoints throughout the session. Upon needle withdrawal, the PSD was removed, and firm pressure was applied to the puncture site using a dry sterile swab to prevent hematoma.

SA Group

The same acupoints and treatment schedule as in the VA group were applied to the SA group. Participants in the SA group underwent a simulated needling procedure using blunt-tipped needles mounted on the PSD (Figure 3). The device was first adhered to the selected acupoints. The acupuncturist then simulated insertion by applying downward pressure on the needle handle. The blunt tip telescoped into the guide tube, creating a palpable ‘pricking’ sensation on the skin surface without penetration. This simulated manipulation mimicked the timing and duration of the VA group to maintain the blind.

Figure 3 Intervention and device diagrams. i. transparent catheter, ii. opaque plastic base, iii. double-sided rubber circle, iv. acupuncture needle, v. blunt needle, vi. Skin.

Outcomes and Assessment

Primary Outcome

The primary outcome was the UCP level on postpartum day 3. A simple and sensitive VAS assessment was used, ranging from 0 to 10 for “no pain” to “most pain”.

Secondary Outcomes

1. The UCP level on postpartum days 1, 2, 10, and 17.
2. The intensity, frequency, and duration of UCP were assessed at five specific time points. The number of days until the disappearance of UCP is also documented. Pain intensity is rated on a 4-point scale from 0 to 3, representing “none” to “severe”.
3. The volume of vaginal blood loss during the initial 72 hours post-enrollment was determined via gravimetric quantification. The researchers weigh the bloody tampons at the time of maternal tampon change and then convert them to volume using the formula: (weight of blood-containing tampons - net weight of tampons (g))/1.05.²⁰
4. The lactation volume score at five specific time points. It is measured using a scale, which 0–3 represents a range from none to more.²¹
5. The Edinburgh Postnatal Depression Scale (EPDS) score on postpartum days 3, 10, and 17. The EPDS has 10 entries, each rated on a 4-point scale from 0 to 3.²² The total score ranges from 0 to 30, and the threshold score for depression is 9. Higher scores indicate more severe depressive symptoms.
6. The Self-Rating Anxiety Scale (SAS) score on postpartum days 3, 10, and 17. The SAS has 20 items covering a wide range of anxiety symptoms. Scores range from 20 to 80, with a threshold of 40, with higher scores indicating greater anxiety.²³
7. The Short Form-36 Health Survey (SF-36) score on postpartum days 3, 10, and 17. The SF-36 consists of 36 items, with scores ranging from 0 to 100. Higher scale scores indicate better quality of life.²⁴
8. Remedial analgesia rate.
9. Participants’ expectations of acupuncture. Before treatment, participants were evaluated their expected effectiveness of acupuncture for pain relief using a 10-point VAS.
10. Participant satisfaction with acupuncture analgesia. It was assessed on days 3 and 17 after enrollment using a 5-point Likert scale.
11. Participant compliance. The number of completed acupuncture sessions and the number of completed assessments at all five time points were recorded for each participant.
12. The success of blinding. After all six treatment sessions, participants were asked to guess their group assignment by choosing among three options: “VA”, “SA”, or “Uncertain”.

Follow-Up

Clinical observation has found that multiparous women may experience UCP lasting up to 16 days postpartum. Additionally, the World Health Organization recommends 7–14 days postpartum as a routine follow-up time.²⁵ Therefore, this study established two follow-up visits on postnatal days 10 and 17 to observe the course of UCP and maternal physical condition. Researchers conducted follow-up calls to inquire about participants’ current status and provide guidance for completing the relevant scales.

Safety Assessment

All adverse events (AEs) related to the study, such as pain, hematoma, infection, etc, were meticulously recorded in the CRF. SAEs were managed by emergency medicine physicians or acupuncturists and were reported to the Medical Ethics Committee. Any medical expenses resulting from AEs caused by the intervention were covered by the study.

Data Collection Methods and Study Monitoring

Raw data were collected at predetermined time points by the same assessor using validated questionnaires and clinical assessment tools and recorded in the CRF. If a participant withdrew from the study, the last available data before their withdrawal were collected and used in the analysis. Two research assistants, who were not involved in the trial, import the collected data into the computer in a suitable form for storage. A data analyst performed the final analysis of the results after collecting all data. The personnel were trained in the standards, ensuring all data are timely, accurate, complete, standardized, and authentic. Data quality was maintained through regular audits and consistency checks. Access to all data involved in this study was restricted to specific personnel. We reported any AEs promptly, and the Ethics Committee reviewed the progress of the study and make adjustments as needed. There was no conflict of interest between this committee and the research project. All raw clinical data will be retained for at least 5 years after publication.

Statistical Methods

Statistical analyses will be performed using SPSS Version 28.0 (IBM Corp., Armonk, NY, USA). We will adhere to the Intention-to-Treat (ITT) principle, incorporating all randomized participants into the final evaluation regardless of protocol adherence. Baseline characteristics will be summarized descriptively: continuous data following a normal distribution will be presented as mean ± standard deviation (SD), whereas non-normally distributed data will be reported as median (interquartile range [IQR]). Categorical variables will be expressed as frequencies and percentages. For all between-group comparisons, continuous variables will be analyzed using independent t-tests or Mann–Whitney U-tests, and categorical variables using Chi-square tests or Fisher’s exact tests. Crucially, for longitudinal data collected at multiple time points (eg, VAS scores), Generalized Linear Mixed Models (GLMMs) will be utilized. Pre-specified confounding factors, including parity and rescue analgesia use (diclofenac, yes/no) will be included as covariates in the primary GLMM model to adjust for potential confounding. Additionally, subgroup analyses by parity will be performed. A two-sided P-value < 0.05 will be considered statistically significant. Appropriate multiple comparison correction will be adopted for pairwise post-hoc analyses where necessary. Missing data will be addressed using multiple imputation techniques.

Confidentiality

To safeguard participant privacy, personal identifiers were replaced with unique alphanumeric codes throughout the study. All collected data remained strictly confidential; unauthorized disclosure to any third party—excluding the attending medical team—was strictly prohibited. Access to CRF was restricted exclusively to authorized personnel responsible for data collection and entry. Furthermore, any disseminated results or public reports will be fully anonymized, ensuring that no individual participant could be identified. Original medical records will be securely archived within the hospital’s database. External access will be granted solely to the investigators, the research authority, and the Ethics Committee, contingent upon the participant’s written informed consent.

Ethics and Dissemination

The study was conducted in full compliance with the Declaration of Helsinki and Good Clinical Practice (GCP) guidelines to safeguard the rights and well-being of all participants. Formal ethical approval for the study protocol and informed consent documents was granted by the Medical Ethics Committee (Approval No. LD2024-001). Research findings will be disseminated through peer-reviewed medical journals. Furthermore, any substantial amendments to the protocol will be submitted to the Ethics Committee for ratification prior to implementation.

Discussion and Conclusion

UCP after vaginal delivery remains a significant clinical challenge, characterized by spasmodic lower abdominal cramping. Given that standard pharmacological treatments may entail adverse side effects, acupuncture emerges as a promising non-pharmacological solution. The pathogenesis of UCP is multifaceted, primarily involving the mechanical compression of nerve terminals and vascular constriction during uterine involution. This process precipitates local hypoxia and hemodynamic disturbances (ischemia-reperfusion), triggering the release of inflammatory algogenic mediators.²⁶ Furthermore, central sensitization of nociceptive pathways may exacerbate the maternal pain experience. Acupuncture is hypothesized to mitigate these processes by modulating endogenous opioid signaling, suppressing neuro-inflammatory excitability, and optimizing pelvic microcirculation, thereby upregulating serum β-endorphin levels.^15,27

To ensure rigorous evaluation, this protocol incorporates a non-penetrating sham control. The blunt-tipped sham needle only elicits a tactile pricking sensation without penetrating the skin, thereby markedly improving the integrity of participant blinding.^28,29 Furthermore, the selection of distal acupoints (ST36, LR3, SP8, GB41) located below the knee minimizes visual cues for supine participants, further fortifying the blinding success.

We selected the VAS as the primary endpoint due to its validated sensitivity and ease of administration in acute pain settings.⁸ Recognizing the physiological link between uterine contractions, lochia discharge, and lactation,^5,6 we employ gravimetric quantification for vaginal bleeding and a standardized lactation score to capture these secondary impacts objectively. This protocol places substantial emphasis on maternal multidimensional well-being; specifically, the SAS and SF-36 are introduced alongside the EPDS to provide a comprehensive profile of how UCP affects mental health and quality of life.

Several constraints warrant consideration. First, the single-center design may restrict the immediate external validity of our findings across diverse populations. Second, the sham device used in the control group is an active control; its tactile stimulation may exert some analgesic effect, potentially attenuating the between-group difference and leading to an underestimation of the observed treatment effect. Third, the inherent nature of manual acupuncture precludes double-blinding of the practitioners. To mitigate this, we have instituted standardized operational protocols and rigorous practitioner training to minimize performance bias. Fourth, although the use of rescue analgesia (diclofenac) will be adjusted for in the statistical analysis and will be reported as a secondary outcome, residual confounding may still exist. Lastly, while subjective scales are robust, future iterations of this research would benefit from the integration of more direct biomarkers to corroborate the subjective analgesic outcomes.

This trial was designed to evaluate the therapeutic efficacy of acupuncture for UCP. Successful implementation will provide evidence-based support for integrating acupuncture into routine postpartum care.