Risk of obstetric anal sphincter injury associated with female genital mutilation/cutting and timing of deinfibulation

Introduction A greater risk of obstetric anal sphincter injury has been reported among African migrants in several host countries compared with the general population. To what degree female genital mutilation/cutting affects this risk is not clear. In infibulated women, deinfibulation prevents anal sphincter injury. Whether the timing of deinfibulation affects the risk, is unknown. This study aimed to investigate the risks of anal sphincter injury associated with female genital mutilation/cutting and timing of deinfibulation in Norway, and to compare the rates of anal sphincter injury in Somali-born women and the general population. Material and methods In a historical cohort study, nulliparous Somali-born women who had a vaginal birth in the period 1990-2014 were identified by the Medical Birth Registry of Norway and data collected from medical records. Exposures were female genital mutilation/cutting status and deinfibulation before labor, during labor or no deinfibulation. The main outcome was obstetric anal sphincter injuries. Results Rates of obstetric anal sphincter injury did not differ significantly by female genital mutilation/cutting status (type 1-2: 10.2%, type 3: 11.3%, none: 15.2% P = 0.17). The total rate of anal sphincter injury was 10.3% compared to 5.0% among nulliparous women in the general Norwegian population. Women who underwent deinfibulation during labor had a lower risk than women who underwent deinfibulation before labor (odds ratio 0.48, 95% confidence interval 0.27-0.86, P = 0.01). Conclusions The high rate of anal sphincter injury in Somali nulliparous women was not related to type of female genital mutilation/cutting. Deinfibulation during labor protected against anal sphincter injury, whereas deinfibulation before labor was associated with a doubled risk. Deinfibulation before labor should not be routinely recommended during pregnancy.