Postpartum perineal pain and dyspareunia related to each superficial perineal muscle injury: a cohort study

To assess the association between superficial perineal muscle trauma and perineal pain and dyspareunia.

Prospective cohort study of 405 women with a spontaneous vaginal birth comparing an intact perineum and first-degree perineal trauma group (n = 205) with a second-degree perineal trauma and episiotomy group (n = 200). Perineal pain was measured at 2 days, 10 days, 7 weeks, 3 months and 6 months postpartum. Dyspareunia was assessed at 7 weeks, 3 months and 6 months postpartum.

All second-degree perineal traumas and episiotomies involved damage to the bulbospongiosus muscle (BSM), but not always to the superficial transverse perineal muscle (STPM). In case of second-degree trauma or episiotomy, the odds of pain at 10 days and dyspareunia at 6 months postpartum were four- and five-fold greater, respectively, than if the perineum had remained intact or suffered a first-degree perineal trauma [OR 4.4 (95% CI: 2.8–6.9) and OR 5.5 (95% CI: 2.8–10.9), respectively]. When comparing injuries where > 50% BSM ± STPM against those with < 50% BSM torn, pain was significantly higher at 10 days postpartum [OR 1.9 (95% CI: 1.1–3.6], with no difference at 7 weeks, while dyspareunia was significantly higher at 6 months postpartum [OR 3.3 (95% CI: 1.4–7.8)]. There was no difference in perineal pain or dyspareunia when comparing first-degree with < 50% BSM traumas.

When perineal muscle trauma encompasses > 50% BSM ± STPM, perineal pain and dyspareunia persisted until 10 days and 6 months postpartum, respectively.