Incidence and Risk Factors for Development of Third and Fourth Degree Perineal Tears: A Four Year Experience in a Single Saudi Center

Background: Vaginal delivery is a physiological process that holds multiple complications. Perineal trauma and vaginal laceration is considered a common complication associated with vaginal delivery. Well established risk factors, recognized by the Royal College of Obstetricians and Gynecologists, are ethnicity, birth weight over 4 kg, persistent occipital posterior position, nulliparity, induction of labor, shoulder dystocia, instrumental delivery. There are other risk factors that were suggested in the literature but data are conflicting, such as Prolonged second stage of labor, episiotomy and obesity Objectives: This study aimed to evaluate third and fourth degree tears rates and the impact of related risk factors on perineal tears in a single Saudi center. Study Design: A retrospective observational cohort study. Methods: This retrospective cohort study analyzed all vaginal deliveries from January 2011 to December 2015 in Security Forces Hospital, Riyadh, Saudi Arabia. The Hospital has around 6000 deliveries per year. Data were extracted from dedicated database software for antenatal care through Hospital System (Medical Record Viewer- MRV) and from Midwife Head Nurse daily record system. Results: During the period of interest 28325 records were identified. Caesarean section was performed in 7322 of them (25.8%). Of the remaining 21003 records, 20300 were included in the study according to the inclusion criteria mentioned above. 56 patients (0.28%) had a severe perineal tear because of delivery and were included in group A (Study Group). Group B (Control Group) consisted of remaining 20244 patients. Univariate analysis indicated the following as risk factors for severe perineal tears: gestational age >40 weeks, nulliparity, moderate/ severe obesity, instrumental delivery, shoulder dystocia, pushing stage >90 min, birth weight >4 kg, head circumference at birth >34 cm and length at birth >50 cm. Risk factors still significant in the final multivariate model were moderate/severe obesity (OR=2.8, CI=1.3-6.1), instrumental delivery (OR=2.6, CI=1.2-5.6) and birth weight (OR=1.1/hg, CI=1.1-1.2). Conclusions: Moderate/severe obesity, vacuum delivery and fetal weight resulted as independent risk factors for severe obstetrical tears.