Introduction
Obstetric anal sphincter injuries (OASI) include third and fourth degree perineal tears and have a major impact on quality of life by resulting in chronic anal incontinence, dyspareunia or perineal pain. OASI may complicate 0.3 to 6 percent of vaginal deliveries related to multiple fetal, maternal and obstetrics factors.1-3 Clinical management of second stage of labour and effectiveness of preventive measures for severe perineal tears are controversial. Operative vaginal delivery is related with increased risk of OASI, reported incidence up to 27% in primiparous women delivering by forceps delivery without an episiotomy.4 Also the risk of OASI is increased approximately 3 times (OR=2.99) times vacuum-assisted delivery.5 Increased maternal age, fetal macrosomia and persisted fetal occipital posterior position are the other risk factors.6, 7
In clinical practice uterine fundal pressure (the Kristeller maneuver) commonly applied in second stage of delivery to accelerate the birth in cases of fetal distress, dystocia, failure to progress in the second stage of delivery, maternal unwillingness to strain due to exhaustion.8 Benefits, reliability and complications of this maneuver are uncertain and real usage frequency may be underestimated owing to medico-legal aspects and adverse outcomes.9 The reported frequency of the manual fundal pressure ranges from 4% to 23% and is frequently used in settings where instrumental deliveries, are not readily available, or cannot be performed because of professional staff shortage.10
Limited availability of endo-anal imaging systems and the development of advanced high-frequency curved array transducers, three-dimensional transperineal ultrasonography (3D-TPU) has attracted attention for its effectiveness in evaluating anal sphincter injury. Three dimensional TPU allows access to the 3 orthogonal planes at same time, tomographic image showing entire sphincter, with minimal patient discomfort and low cost.11 Exoanal 3D-TPU imaging have validity and repeatability for anal sphincter injuries in parallel to improving of image quality and software of 3D ultrasound systems.12
Identification of avoidable risk factors of OASI is important to avoid unnecessary interventions which may cause long term morbidity. Therefore, the aim of this study was to evaluate the effect of using uterine fundal pressure during the second stage of delivery on OASI among primiparous women using 3D-TPU exoanal imaging.