Risk factors of uterine rupture with a special interest to uterine fundal pressure

PURPOSE Uterine rupture is a rare but serious event with a median incidence of 0.09%. Previous uterine surgery is the most common risk factor. The aim of our study was to analyze retrospectively women with uterine rupture during labor and to evaluate postulated risk factors such as uterine fundal pressure (UFP). METHODS Twenty thousand one hundred and fifty-two deliveries were analyzed retrospectively. Inclusion criteria were 22 weeks and 0 days-42 weeks and 0 days of gestation, singleton pregnancy and cephalic presentation. Women with primary cesarean section were excluded. A logistic regression analysis adjusting for possible risk factors was conducted and a subgroup analysis of women with unscarred uterus was performed. RESULTS Twenty-eight cases of uterine rupture were identified (incidence: 0.14%). Uterine rupture was noticed in multipara patients only. In the multivariate analysis among all study patients, only previous cesarean section remained a statistically significant risk factor [adjusted odds ration (adj. OR) 12.52 confidence interval (CI) 95% 5.21-30.09]. In the subgroup analysis among women with unscarred uterus (n=19,415) three risk factors were associated with uterine rupture: UFP (adj. OR 5.22 CI 95% 1.07-25.55), abnormal placentation (adj. OR 20.82 CI 95% 2.48-175.16) and age at delivery >40 years (adj. OR 4.77 CI 95% 1.44-15.85). CONCLUSIONS The main risk factor for uterine rupture in the whole study population is previous uterine surgery. Risk factors in women with unscarred uterus were UFP, abnormal placentation, and age at delivery >40 years. The only factor which can be modified is UFP. We suggest that UFP should be used with caution at least in presence of other supposed risk factors