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.