2 meshes. All procedures were performed in the urogynaeco- logical unit. Data for the statistical analysis was obtained from the urogynaecological unit database collecting all cases of TVT. The primary outcome was occurrence of bladder injury and urinary retention. Bladder injury was deﬁned as injury caused by trocars for introduction of TVT conﬁrmed with perioperative cystoscopy. Urinary retention was deﬁned as an inability to pass urine of 200 mL within 6 hours of TVT procedure or postvoiding volume of more than 150 mL. BMI (kg/m2), age, type of analgesia, concomitant prolapse repair, and previous surgery were studied factors. General anaesthesia, spinal anaesthesia, and sedation with local anaesthesia were used for TVT procedures. After assuring that a distribution of BMI across categories of complications was equal, study cohort was stratiﬁed to two subgroups by BMI (<30 and ≥30). Medians and interquartile ranges were used to describe continuous variables and the Mann-Whitney U test and the Kruskal-Wallis test were used for comparisons of continuous data. Chi-square test was used for univariate analysis of categorical data to compare subgroups and to establish a relationship between BMI and bladder injury or urinary retention. This was followed by a multivariable regression analysis to adjust this relationship for age, concomitant surgery, type of analgesia, and previous surgery. Unadjusted and adjusted odds ratios with 95% conﬁdence intervals (CI) were calculated. Statistical analysis was performed using SPSS computer software (statistical package for the social sciences, version 16.0). 3. Results Study population of 342 cases of TVT procedures were analysed during the period of 2001–2008. The incidence of bladder injury was 4.7% (16/342) and the rate of urinary retention was 9% (31/342). Cohort was stratiﬁed into two subgroups by body mass index (<30, ≥30) with following description: n = 246 (72%) and 96 (28%), respectively, and median 25.5 with an interquartile range (23–27) and 33 (31–35), respectively. There was no statistically signiﬁcant diﬀerence in the cohort characteristics by BMI subgroups (age, concomitant procedure, type of analgesia, previous surgery, and complications) (Table 1). The distribution of BMI was the same across categories of complications (the Kruskal-Wallis test, P = 0.675). Neither univariate analysis nor multivariate regression analysis revealed any statistically signiﬁcant inﬂuence of BMI (<30, ≥30) on the incidence of bladder injury or urinary retention (Table 2). Unadjusted odds ratios (OR) and adjusted odds ratios (adj. OR) for bladder injury and urinary retention by BMI groups were OR 1.7296 CI 0.4818–6.2097; OR 1.3745 CI 0.5718–3.3043 and adj. OR 2.885 CI 0.603–13.8; adj. OR 1.299 CI 0.502– 3.365. Posthoc statistical power analysis was performed using McFadden R-Squared 0.085, with statistical power 0.996. 4. Discussion In 2003, Department of Health estimated prevalence of overweight and obese women to 56%. Further 26% raise in Obstetrics and Gynecology International Table 1: Characteristic of cohort by body mass index (BMI). BMI <30 (n = 246), ≥30 (n = 96), 72% 28% 54 (45–64) 55 (44.75–64) 75 (78%) 13 (14%) 8 (8%) 4 (4%) 38 (40%) 54 (56%) 88 (92%) 4 (4%) 3 (3%) 1 (1%) 86 (90%) 3 (3%) 7 (7%) P value .7837 .51 .5254 .9732 .9314 .689 .8073 .599 .8803 .9314 .8659 .3466 .5722 .6145 Characteristics Median (IQR) age Concomitant procedure No. A&P repair VH and repair Analgesia GA Spinal Sedation Previous surgery No. TAH VH and repair Burch Complications No. Bladder damage Retention of urine 182 (74%) 42 (17%) 22 (9%) 8 (3%) 105 (43%) 133 (54%) 219 (89%) 13 (5%) 9 (4%) 5 (2%) 209 (85%) 13 (5%) 24 (10%) IQR: interquartile range; A&P: anterior and posterior; GA: general anaes- thesia; TAH: total abdominal hysterectomy; VH: vaginal hysterectomy. obesity occurred in 2010 [11]. This epidemic increase will put strains on urogynaecological services. In this light, it is important to predict the impact of BMI on procedures such as TVT. Several studies produced conﬂicting ﬁndings of the eﬀect of BMI on perioperative and postoperative complications. Two studies reported on increased incidence of a bladder injury with BMI less than 30 kg/m2 [12, 13]. Nevertheless, ﬁrst study was underpowered due to a small sample size of only 198 women and results were not adjusted using multivariable regression analysis [12]. Further reports described no eﬀect of BMI on com- plication rates for vaginal hysterectomy or TVT [14–16]. Our study, with its larger sample size and statistical power using multivariable regression analysis, further reinforces ﬁndings of no eﬀect of BMI on incidence of bladder injury and urinary retention. Multivariable regression analysis has become a standard statistical method for analysis of retrospective studies in obstetrics and gynaecology as it is a useful way of describing the relationship between one or more potential risk factors such as obesity and an outcome such as bladder injury [17, 18]. There are some sources of potential bias in this study. Data was collected retrospectively from the hospital database, so there is a chance some data could have been entered inconsistently. However, this means that data were entered without knowledge of a study hypothesis therefore reducing the risk of bias. There may be additional outstanding factors that could have an eﬀect on the results that have not been