Perineal tears are considered to be one of the most prevalent injuries during childbirth, affecting approximately 80% of primiparous women [1]. The perineal body, a complex structure where the transverse perineal muscle, the puboperinealis muscle, and the puboanalis muscle (both parts of the levator ani muscle) fuse with fascial structures, is located in the perineal area. The perineal body’s integrity is essential for pelvic organ support.

Recent research shows that symptoms of a wide vagina, vaginal flatulence, bowel-emptying difficulties, and sexual dysfunction are associated with a deficient perineum after birth [2]. These findings resulted in the development of the questionnaire “Karolinska Symptoms After Perineal Tears Inventory” (KAPTAIN) to help clinicians identify women with an injury in the perineum [2]. 

However, the anatomy of the perineum is complex. To get a better understanding of this area, we have presented a reliable protocol for assessing childbirth-related deviations in the muscles at the level of the perineal body using three-dimensional endovaginal (3D EVUS) and endoanal ultrasound (3D EAUS) in women one year after birth [3]. Whether these deviations are of clinical importance needs further investigation. 

Therefore, the aim of this study was to investigate whether primiparous women with sonographic deviations in the perineal muscles reported more symptoms using the KAPTAIN score compared to women without sonographic deviations one year after birth.

In this prospective cohort study participants were included at 18-20 weeks of pregnancy. Of the 609 primiparous women included in pregnancy, 36 participants were excluded and 185 participants were lost to follow-up, leaving 388 eligible for analysis. Symptoms were assessed using KAPTAIN, answered electronically at inclusion in pregnancy and one year after birth. KAPTAIN consists of 11 questions with a 4-point scale response option, giving a maximum sum score of 33 [2]. A cut-off value of ≥ 8 was set as a reference for clinically relevant symptoms of a deficient perineum [2]. Background and obstetric data were gathered from hospital records.

The women were examined one year after birth at the hospital’s outpatient clinic with 3D EVUS and 3D EAUS using a BK 5000 machine with a high-resolution probe. The volumes were stored for offline analysis and analyzed according to the analysis protocol developed by the research team where high reliability has been found [3]. One investigator analyzed all volumes, blinded to the women’s obstetric history. The muscles transverse perineal, the puboperinealis, and the puboanalis were identified at the area where they fuse into the perineal body and evaluated for the presence of a deviation. A deviation was defined as a muscle discontinuity on the right side, the left side, or centrally, detectable in at least two ultrasound planes, or if a muscle was not visible. 

Exposure measure was the diagnosis of sonographic deviation in at least one of the perineal muscles at the area where they fuse into the perineal body. The outcome measure was a KAPTAIN score ≥ 8.

Descriptive statistics were used for baseline data and deviations in the perineal muscles. KAPTAIN score was presented as median with quartiles. The association between muscle deviations and the KAPTAIN score ≥ 8 was analyzed using logistic regression.

Background information and obstetric data are presented in Table 1. The cesarean section rate was 16.5%. Thirty-eight percent of the participants had a second-degree perineal tear, and 33% had an episiotomy. At inclusion in pregnancy, 28 (7.2%) participants had a KAPTAIN score ≥ 8.

One year after birth, 168 participants (43.3%) had a detected sonographic deviation in one or more of the perineal muscles fusing into the perineal body. Their median KAPTAIN score was 6.0 (quartiles 3.0-9.0). Participants with an intact perineum had a median score of 4.0 (quartiles 2.0-6.0). 

Out of the 168 women with at least one sonographic muscle deviation, 54 (32.1%) had a KAPTAIN score ≥ 8. Thirty-one (14.1%) of the participants without sonographic deviation had a KAPTAIN score ≥ 8. The odds ratio (OR) of reporting av KAPTAIN score ≥ 8 was 2.9 (95% CI 1.7-4.7) higher for the group of women with at least one muscle deviation compared to women with sonographic intact perineum. This association was also significant when adjusting for age, BMI, KAPTAIN score in pregnancy, vacuum delivery, cesarean section, and ultrasound-verified levator ani avulsions with an OR of 2.3 (95% CI 1.2-4.2).

This is the first study testing the association between the novel questionnaire specifically designed to capture childbirth-related symptoms of perineal injury and the new ultrasound methodology using 3D EVUS and 3D EAUS giving access to the complex muscle structures of the perineum. Our study found an association between symptoms related to perineal deficiency and the detection of deviations in the perineal muscle one year after birth. Given the intricate anatomy of the perineum, relying solely on a standard gynecological examination might be insufficient to obtain enough information on the perineal part of the pelvic floor muscles. In these cases, ultrasound of the perineal muscles can offer valuable and clinically relevant insight.

There is an association between sonographic deviation in the perineal muscles using 3D EVUS and 3D EAUS and symptoms captured by the KAPTAIN one year after birth.

Macedo MD, Risløkken J, Halle T, Ellström Engh M, Siafarikas F. Occurrence and risk factors for second-degree perineal tears: A prospective cohort study using a detailed classification system. Birth. 2024.
Rotstein E, von Rosen P, Karlström S, Knutsson JE, Rose N, Forslin E, et al. Development and initial validation of a Swedish inventory to screen for symptoms of deficient perineum in women after vaginal childbirth: 'Karolinska Symptoms After Perineal Tear Inventory'. BMC Pregnancy Childbirth. 2022;22(1):638.
Lilleberg H, Starck M, Bø K, Engh ME, Siafarikas F. Childbirth related deviations to perineal anatomy assessed by three-dimensional endovaginal ultrasound: A reliability study.  ICS; Sept 27-29; Toronto, Canada 2023.

Continence 12S (2024) 101392
DOI: 10.1016/j.cont.2024.101392