Background:Obstetric anal sphincter injuries (OASIS) can cause an adverse impact on women's physical and mental health. There was lack of published data in Chinese population particularly on studying the risk of OASIS for nonrotational outlet forceps. This study was to determine the incidence and risk factors of OASIS.Methods:This is a retrospective cohort study carried out in a tertiary referral hospital in Hong Kong. The control group was selected randomly. Univariate and multivariate logistic regression analysis was performed to evaluate the influence of potential risk factors on OASIS. This study reviewed the obstetric records of OASIS women and random control from January 2011 to June 2014. Univariate and multivariate logistic regression analysis was performed to evaluate the influence of potential risk factors on OASIS.Results:Of 15,446 women delivered, 49 had OASIS. The percentage of OASIS increased from 0.3% (2011) to 0.38% (2014). There was an increasing trend of OASIS in attempted spontaneous vaginal delivery without episiotomy (P < 0.01), but it did not increase the OASIS risk (P = 0.46). Univariate analysis of 49 cases and 438 control subjects showed that forceps delivery (odds ratio [OR] =8.73, P < 0.01), prolong second stage of labor (OR = 1.43, P < 0.01) increased the risk for OASIS. In multivariate regression models, only forceps delivery (OR = 6.28, P < 0.01) proved to be independent risk factor.Conclusions:The incidence of OASIS in Chinese women was increased after 2012, but still lower than the reported figures in the literature. Outlet forceps delivery could be a possible associated risk factor.

In published work review, extracorporeal shock wave therapy (ESWT) has been showed to be effective in treating chronic perineal/pelvic pain in men, but there was no published report on its use in women. We report a case of female chronic perineal pain successfully treated by ESWT. A 51-year-old woman presented with persistent perineal scar pain after excision of a vulval-vaginal nodule despite oral analgesics and gabapentin. After 11 cycles of ESWT, she reported termination of analgesics consumption and decreased perineal pain score from 8 to 2. The Short Form 36 Questionnaire demonstrated improvement in physical and mental health conditions. There was no complication encountered. We postulate that the effect of ESWT in this patient was based on reduction of muscle tone and alternating the threshold of pain memory, similar to the mechanisms in male patients. Further study is required to determine the use of ESWT in treating female chronic perineal pain.