Eley VA, et al. - The failure rate of epidural extension in obese and non-obese women was compared in a prospective cohort and risk factors for extension failure were also investigated. One hundred obese participants (Group O, body mass index ≥ 40 kg/m²) were prospectively identified and allocated two sequential controls (Group C, body mass index ≤ 30 kg/m²). Using Chi-squared and logistic regression, risk factors for extension failure were identified. Ineffective labor analgesia requiring anesthesiologist intervention, and BMI > 50 kg/m² were identified as risk factors for failure in obese women. Between the groups, no significant difference was found in the failure rate of epidural extension.