Operative delivery options in the second stage of labour : optimizing maternal and perinatal safety

Increased operative vaginal delivery, using obstetric forceps and/or vacuum, has been recommended in an effort to curb the rising rate of cesarean delivery. However, the comparative perinatal and maternal safety of operative vaginal delivery and cesarean delivery is not clear. This dissertation aimed to quantify rates of severe perinatal and maternal morbidity and mortality following operative vaginal delivery and cesarean delivery. The studies in this dissertation were based on information from Canadian national and provincial population-based health databases and included women who delivered a singleton term infant by operative vaginal or cesarean delivery between 2003 and 2014. Study sizes varied from 10,901 to 1,938,913. Logistic regression, propensity score analysis and ecological Poisson regression were used to estimate adjusted rate ratios (ARR) with 95% confidence intervals (CI). Midpelvic operative vaginal delivery was associated with an increased risk of severe perinatal morbidity/mortality compared with cesarean delivery, although this association varied based on instrument applied and indication for operative delivery. For example, among deliveries with dystocia, midpelvic operative vaginal delivery was associated with higher rates of severe perinatal morbidity/mortality compared with cesarean delivery (forceps ARR 2.11, 95% CI 1.46-3.07; vacuum ARR 2.17, 95% CI 1.49-3.15). Among deliveries with fetal distress, the risk of severe maternal morbidity/mortality was higher with midpelvic forceps and lower with midpelvic vacuum. However, rates of obstetric trauma were high following operative vaginal delivery, irrespective of instrument or indication. Rates of birth trauma and obstetric trauma were significantly increased after operative vaginal delivery at all pelvic stations. Further, the population (ecological) rate of operative vaginal delivery was positively associated with the rate of obstetric trauma and the rate of severe birth trauma: a one percent increase in the operative vaginal delivery rate resulted in over 700 additional cases of obstetric trauma per year among nulliparous women. Encouraging higher rates of operative vaginal delivery as a strategy to prevent cesarean delivery may result in higher rates of perinatal and maternal morbidity/mortality, especially birth trauma and obstetric trauma. The risks and benefits of both operative vaginal and cesarean delivery should be clearly communicated to women, ideally in the antepartum period.Medicine, Faculty ofPopulation and Public Health (SPPH), School ofGraduat