TECAR in the Management of Early Postpartum Perineal Pain.

The study used the Winback Back S1 device (max. 100W, 500 and 300 kHz frequency), which operates in Resistive Energy Transfer (RET) and Capacitive Energy Transfer (CET) modes. To standardize participants' sensations and enhance blinding, a non-thermal current dose was predetermined at 10% intensity for RET and 20% for CET, based on application to the abdominal wall in 20 volunteers. Due to reduced intensity, the treatment duration was prolonged to match the therapeutic efficacy reported with shorter application times and higher intensities, as documented in previous studies on pelvic floor rehabilitation, sports physiotherapy, and data from the TECAR training program. Both the INT and SHAM groups received two TECAR sessions. The CON group underwent the same assessment as INT and SHAM, but was only observed without therapeutic intervention. This allowed for characterization of natural postpartum recovery and comparison with the other groups. Adverse events were assessed systematically after each treatment session by asking all participants about pain, discomfort, skin irritation, burns, or any other unexpected symptoms.

Data collected from participants encompassed both clinical and demographic information, such as age, body mass index (BMI), parity, and delivery-related factors. Information about the duration of the first and second stages of labor, type of pregnancy (singleton or multiple), use of vacuum extraction or forceps, classification of perineal trauma, newborn birthweight and length, fetal position at birth, and the method used for perineal suturing were recorded. The number and type of analgesics (eg, paracetamol, ibuprofen, or others) taken within the first 48 hours postpartum were recorded. The Incontinence Severity Index (ISI) was used to assess urinary incontinence severity, based on symptoms experienced at the end of pregnancy. ISI assesses two dimensions of urinary incontinence: the frequency of leakage (ranging from never = 0 points to every day = 4 points) and the amount of urine leakage (ranging from drops = 1 point to more than small splashes = 3 points).

A physiotherapist trained in pelvic floor health with at least 5 years of experience performed a visual observation of the perineum and a transvaginal pelvic floor muscle examination. This included assessing muscle strength using the Modified Oxford Scale (ranging from 0 to 5), measuring endurance (up to 10 seconds) and response speed (up to 10 rapid contractions), following the abbreviated PERFECT scheme.

Pain and perineal discomfort at rest, while sitting, and while walking were assessed using the Numeric Rating Scale (NRS) at three time points: before the intervention (baseline), and on the day following both the first (post1) and second (post2) intervention sessions. Participants in all groups received a take-home observation sheet for the six weeks of the postpartum period. They recorded the highest levels of perineal pain, discomfort, and the total number of analgesics taken, administered during each of the six postpartum weeks (puerperium1-6). Participants were informed about planned telephone and email communications to arrange the postpartum visit.

A follow-up visit was performed 6 to 8 weeks postpartum at the outpatient clinic, during which pelvic floor muscle function was re-evaluated. Participants were asked to provide information from the postpartum period, including ISI. Those unable to attend in person were asked to email their completed observation sheets.

Randomization was performed using the simple randomization method. The main researcher used a computer-generated random number sequence to allocate participants individually to either the intervention (INT) or SHAM group. Group assignments were concealed from both participants and study personnel involved in outcome assessment (double-blind design). The device did not have an in-built randomization function, and participants were blinded to group allocation until the end of the study. To ensure blinding during the intervention, the device was paused and covered from the participant's view. The control group (CON) was enrolled after recruitment of the INT and SHAM groups, thereby forming a distinct time cluster in the recruitment process without randomization to track the natural healing process.

The primary outcome of this study was the change in pain level at rest, sitting, and walking measured at baseline, after each intervention, and weekly during the postpartum period, and compared across the INT, SHAM, and CON groups.

The secondary outcomes were:

• changes in perineal discomfort in sitting and walking, assessed at baseline, after each intervention, and weekly during the postpartum period, compared between the study groups;
• doses of paracetamol and ibuprofen administered in the first days after childbirth and in the subsequent weeks of the postpartum period, compared between the study groups;
• changes in ISI scores assessed at baseline and at the 6-8 week follow-up, compared between the study groups;
• changes in pelvic floor muscle function, assessed at baseline and at the 6-8 week follow-up, compared between the study groups.

The sample size was calculated based on the primary outcome, which was the change in pain intensity. The required sample size was estimated using the G*Power software (version 3.1., University of Düsseldorf, Germany) for an F test (ANOVA: repeated measures, between factors) with three groups and two measurement points (before and after the intervention). The sample size calculation aimed to detect a 1.0 point clinically relevant difference (SD=1.5) with 90% power and a two-sided α = 0.05, assuming a medium effect size (f=0.25). The estimated minimum sample size was 52 participants per group (total n=156). With an anticipated 10% dropout rate, the required sample size increased to at least 58 participants per group (n=174). The dropout rate was approximately 50%. However, missing parameters were estimated using full information maximum likelihood (FIML), eliminating the need for data imputation. Therefore, drop-out cases did not result in the exclusion of participants from the analysis across the entire puerperium and did not significantly reduce statistical power. Statistical analyses were conducted using Python (pandas, stats models) and additional statistical software as needed. Data normality was assessed using the Shapiro-Wilk test. For baseline comparisons between groups, one-way analysis of variance (ANOVA) was applied for continuous variables. If the distribution significantly deviated from normality, the Kruskal-Wallis test was used as a non-parametric alternative. Categorical variables were compared using the chi-squared test or Fisher's exact test, as appropriate.