Vaginal palpation versus transabdominal ultrasound in the comprehension of pelvic floor muscle contraction after vaginal delivery: a randomised controlled trial

This two-arm randomised controlled trial was conducted in three facilities in Tokyo, Japan, in women who gave birth in primary facilities, such as midwifery home and gynaecology clinic. Data were collected between July 2018 and January 2019. The eligibility criteria were as follows: (1) age ≧ 20 years; (2) vaginal delivery; and (3) 4–6 weeks after term delivery. Women were excluded from the study if (1) they had previously received guidance for PFM contraction via VP or TAU; (2) they deviated from a normal status of obstetrics and urology; (3) they had perineal pain or numbness at the time of intervention; (4) they had urinary nerve damage; and (5) they were not able to read and write in Japanese.

This trial was registered with the UMIN Clinical Trials Registry (registration no. UMIN000032304).

The participants were assigned to either the VP or TAU group. The randomisation involved centralised allocation managed by a web-based randomisation system with permuted blocks of four. Due to the nature of the intervention, masking of the intervener and participants was not possible, and the data were not masked by assignment during the analysis.

The intervention was performed by the intervener (midwife) alone, who implemented either the technique of VP by touching the PFMs in the VP group or TAU by showing an extracted image in the TAU group. The details of each teaching protocol are as follows.

To ensure uniformity and objectivity of each intervention, the teaching instructions were integrated according to specific protocols. However, the instructions that were similar in both groups were as follows:

Changes in the pre- and post-intervention comprehension of PFM contraction were assessed by changes in the displacement of the bladder base during contraction and changes in understanding the contraction. Changes in bladder base displacement were measured using TAU pre-intervention, and post-intervention changes were measured similarly after a 5-min break. The measurement was performed without showing the ultrasound screen to the participants to avoid any visual feedback effect. The TAU probe was placed in the mid-sagittal plane immediately supra-pubically on the lower abdomen [11]. The measurement point was a clearly defined edge of maximum displacement of the fascia between the interureteric ridges in the bladder base and bladder neck [17, 18], and the distance between PFM relaxation and contraction was measured in mm using an on-screen calliper. The participants performed three repetitions of maximum voluntary contractions for 3 s with 10 s of relaxation between each contraction, and the mean value was used in the statistical analysis [19]. TAU is valid and reliable in assessing PFM function, and different bladder volumes do not influence the displacement measures; therefore, a strict bladder filling protocol was not necessary [20]. TAU was performed using LOGIQeV2 (GE Healthcare Japan Corp, Tokyo, Japan) with a 3.5–5.5-MHz curved array transducer. A representative image of the displacement of the bladder base during PFM contraction is shown in Fig. 1.

Pre- and post-intervention changes in understanding PFM contractions were assessed using a two-item questionnaire, which included the questions ‘Do you know where to contract in the body?’ and ‘Do you understand the sensation of contracting the pelvic floor muscles?’, as previously reported [21]. The questionnaire used a five-point Likert scale (1–5 points), and a higher score indicated better understanding.

Prior to the intervention, urinary incontinence was assessed using the Japanese version of the International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF), which was created through the process of linguistic validity verification, and its reliability and validity have been previously verified [22]. We have obtained permission to use the Japanese version of ICIQ-SF. We also collected information on the frequency of PFM training and demographic information about the participants.

Statistical analyses were performed using SPSS Statistics v24 for Windows (IBM Inc., Armonk, NY, USA). Comparisons of the demographic data, ICIQ-SF scores, and frequency of PFM training were performed using the chi-square test and t-test. Changes in the comprehension of PFM contraction between the groups were compared using the Welch’s t-test.

The sample size was calculated based on a previous randomised controlled study that verified the effects of PFM training in women with pelvic organ prolapse [23]. In that study, the intervention group received individual training by a physiotherapist for 6 months, and the control group received guidance as usual; the resting position of the bladder increased by a mean of 4.2 mm [95% confidence interval (CI), 2.8–5.6] in the intervention group and − 0.1 mm (CI, − 1.9 to 1.6) in the control group. Therefore, for an effect size of 0.75, power of 80%, and significance level of 0.05, the estimated sample size was 28 women in each group.

For this study, 471 eligible postpartum women were identified between July 2018 and January 2019. When the sample size was reached, the recruitment was stopped. Four women were excluded before randomisation because they were not within the 4–6 weeks postpartum period, and 402 women refused the invitation to participate. Therefore, a total of 65 women participated in the study; 32 were allocated to the VP group and 33 to the TAU group. After random assignment, there was no dropout until the end of the study, and all of the 65 participants were included in the outcome analysis (Fig. 2).

Baseline data comparison revealed no differences between the two groups in all items, including the demographic data, frequency of PFM training, status of urinary incontinence, and ICIQ-SF score (Table 1).

The mean ± standard deviation (SD) bladder base displacement before the intervention was 5.80 ± 4.69 mm in the VP group and 6.04 ± 5.05 mm in the TAU group, which were not significantly different. After the intervention, the bladder base displacement was 6.91 ± 3.31 mm in the VP group and 6.19 ± 4.05 in the TAU group. The change in bladder base displacement was greater in the VP group (1.11 ± 2.34 mm) than in the TAU group (0.15 ± 3.28 mm); however, the difference was not statistically significant (Table 2).

In the two-item questionnaire to assess the understanding of PFM contraction, the question ‘Do you know where to contract in the body?’ was answered as ‘Hard to understand’ by nine participants and ‘Did not understand’ by one participant in the VP group before the intervention. The question ‘Do you understand the sensation of contracting the pelvic floor muscles?’ was answered with ‘Hard to understand’ by eight participants and ‘Did not understand’ by two participants, in the VP group before the intervention. After the intervention, both items of the questionnaire were answered by all 32 participants in the VP group as either ‘Extremely well’ or ‘Moderately well’. In contrast, the first question was answered with ‘Hard to understand’ and ‘Did not understand’ by five and two participants in the TAU group, respectively, before the intervention. The second question was answered with ‘Hard to understand’ by eight participants in this group. After the intervention, in the TAU group, two participants answered the first question with ‘Hard to understand’, one of whom also answered the second question with ‘Hard to understand’. Nevertheless, there was no statistically significant difference between the two groups regarding the changes in the understanding of PFM contraction after implementation of the two teaching methods (Table 3).

Participants with perineal injuries or urinary incontinence were sub-grouped and analysed to determine the differences in the results according to the teaching method.

Participants in the VP and TAU groups were subdivided into two sub-groups according to the presence or absence of perineal injuries (episiotomy or laceration)—the perineal injury group and perineal intact group (Table 4). Seventeen participants in the VP group and 18 in the TAU group had perineal injuries. Women who had perineal injuries (episiotomy or laceration) received sutures for the same. Pre-test bladder base displacement was similar between the groups. Before and after the intervention, bladder floor displacement was larger in the perineal intact group than in the perineal injury group. Specifically, the change in bladder floor displacement after the intervention in participants in the VP group with perineal injuries was 1.55 ± 2.71 mm, while that in participants in the TAU group with injuries was − 0.10 ± 4.08 mm, which were not statistically significantly different. Furthermore, the change in women without injuries (perineal intact group) was 0.61 ± 1.80 mm in the VP group and 0.46 ± 2.02 mm in the TAU group, with no statistically significant differences between the two groups.

Similarly, participants in the VP and TAU groups were subdivided into the incontinent and continent group depending on the presence or absence of urinary incontinence, respectively (Table 5). Thirteen participants (40.6%) in the VP group and 14 (42.4%) in the TAU group had urinary incontinence. Bladder base displacement before the intervention was comparable between the groups. Unexpectedly, both before and after the intervention, the bladder base displacement was larger in the incontinent group than in the continent group. Specifically, the change in bladder floor displacement after the intervention in participants in the incontinent group was 0.75 ± 2.09 mm in the VP group and − 0.95 ± 2.93 mm in the TAU group with no statistically significant differences between the two groups. Furthermore, the change in bladder floor displacement after the intervention in participants in the continent group was 1.35 ± 2.52 mm and 0.96 ± 3.35 mm in the VP and TAU groups, respectively, although no statistically significant differences were observed between the two groups.

No adverse events associated with the two interventions were reported by the participants.

This study had a few limitations. First, it was not possible to mask the group allocation. Second, we did not investigate whether the intervention was being implemented continuously as we compared the changes in the participant’s comprehension of PFM contraction with each teaching method. Future research is needed to evaluate the study outcomes after continuing PFM training for a longer duration. Finally, since the participants were low-risk postpartum women, it is necessary to also consider high-risk participants in the future.