Pelvic floor pain and dyspareunia are both important entities of postpartum pelvic pain, often concomitant and associated with perineal tears during vaginal delivery. However, the association between postpartum endosonographically diagnosed anal sphincter defects, pelvic floor pain, and dyspareunia has not been fully established. The association between sonographic defects and anal incontinence is well known (1), and one study aimed at evaluating parturition mode recommendations following obstetric anal sphincter injuries found that dyspareunia was more common in patients with residual external anal sphincter defects (2). We aimed to determine the prevalence of postpartum anal sphincter defects using three-dimensional endoanal ultrasonography (3D-EAUS). The primary outcome was association of postpartum sonographic sphicter defects with symptoms of pelvic floor pain and dyspareunia. Secondary outcome was risk factors for postpartum sonographic anal sphicter defect.

This study was part of a large interdisciplinary project involving birth-related perineal injuries, endoanal ultrasonography and postpartum pelvic floor disorders. The present study is a prospective cohort study that followed 239 primiparas from birth to 12 months postdelivery. Anal sphincters were assessed with 3D- EAUS three months postpartum. Volume recording was performed by a trained midwife in a specialized outpatient clinic, using a Flex Focus 500 Ultrasound Machine (BK Medical ApS, Herlev, Denmark) with an 8838 axial endoscopic probe at 12 MHz. Endosonographic datasets were analyzed using proprietary software (BK viewer) on a personal computer by one of the authors who was blinded to all clinical, demographic, and delivery data. A sonographic sphincter defect was defined as a discontinuity in the endosonographic image of the internal anal sphincter (IAS, hypoechoic ring) or external anal sphincter (EAS, mixed echoic ring) and/or characterized by the loss of normal architecture in the appearance of the IAS and/or EAS on ultrasonography. Self-reported pelvic floor function data were obtained using a web-based questionnaire distributed one year after delivery. Adaptive questioning processes were used in cases where supplementary questions addressed further specifications regarding the occurrence of symptoms such as dyspareunia. The scored items of the questionnaire were validated. The survey was conducted voluntarily, and the patient provided consent by logging in with their individual code and submitting the results. Descriptive statistics were compared between the patients with and without sonographic defects, and the association between sonographic sphincter defects and outcomes were analyzed using logistic regression. Analysis of power was performed in the initial study of the project; because the current study is a follow-up study involving the same cohort, power analysis was not applicable. STROBE guidelines were followed. An image of a sonographic anal sphincter defect 3 months postpartum is presented in Figure 1.

At three months postpartum, 48/239 (20%) patients had sonographic anal sphincter defects on 3D-EAUS, of which 43 (18%) were not clinically diagnosed with obstetric anal sphincter injury at the time of delivery. Patients with sonographic defects had higher fetal weight than those without defects, and a perineum <2 cm before the suture was a risk factor for defects (odds ratio [OR], 6.9). One year after delivery, most of the patients were sexually active; however, 30 (13%) had no active sexual relations. Patients with sonographic defects had a higher probability of not having sexual relations (OR, 3.4; 95% CI, 1.4–8.0). Dyspareunia was experienced by 39% of the patients who were sexually active. Additionally, the risk of experiencing dyspareunia was elevated in those with defects (OR, 2.4; 95% CI, 1.4–8.0). The feeling of being too tight (15%) was more common than the feeling of being too wide (9%), with no statistical differences between the groups; however, feeling too tight was reported by 24% in the defect group. 
Perineal pain was experienced by 33 (15%) patients, and 14 reported pain severe enough to prevent most activities in the last three months. Perineal pain was present in both groups, with an elevated risk in the defect group (OR, 2.3; 95% CI, 1.0–5.1). Of those with perineal pain (n=33), 22 were sexually active and nine had no sexual relations. The coexistence of dyspareunia and perineal pain in sexually active women is presented in Figure 2.

A sonographic defect on postpartum endoanal ultrasound is a potential prognostic factor for future pelvic floor pain and/or sexual dysfunction, indicating that ultrasonographic imaging may be beneficial during postnatal follow-up. Additionally, a perineal height <2 cm, measured by bidigital palpation immediately postdelivery, was a significant risk factor for sonographic anal sphincter defects. These findings have implications for the clinical setting, including addressing these issues in the early postnatal period to avoid the development of chronic pain, as well as for auditing repair and secondary prevention. Evidence from other studies suggests that sonographic follow-up at 10–12 weeks postpartum in high-risk patients might reduce the morbidity arising from perineal tears (3).

In summary, our findings suggest an association between postpartum sonographic anal sphincter defects, pelvic floor pain, and dyspareunia. Patients at risk of developing pelvic pain and dyspareunia should be identified early in the post-partum period to initiate adequate treatment. A multimodal approach to address all aspects of pain is suggested.

Starck M, Bohe M, Valentin L. The extent of endosonographic anal sphincter defects after primary repair of obstetric sphincter tears increases over time and is related to anal incontinence. Ultrasound Obstet Gynecol. 2006;27:188-197.
van der Vlist, M., Oom, D., van Rosmalen, J. et al. Parturition mode recommendation and symptoms of pelvic floor disorders after obstetric anal sphincter injuries. Int Urogynecol J 31, 2353–2359 (2020)
Bellussi F, Dietz HP. Postpartum ultrasound for the diagnosis of obstetrical anal sphincter injury. Am J Obstet Gynecol MFM. 2021;3:100421.

Continence 7S1 (2023) 100821
DOI: 10.1016/j.cont.2023.100821