Maternal Body Mass Index and Regional Anaesthesia Use at Term: Prevalence and Complications

Background: There is an evidence gap regarding the use of regional anaesthesia (epidural, spinal, or combined epidural/spinal anaesthesia) and associated complications by maternal body mass index (BMI). We examine associations between regional anaesthesia, mode of delivery, and regional anaesthesia complications by pre-pregnancy BMI categories among term deliveries. Methods: Retrospective cohort study of births in California, 2007-2010, utilizing linked birth certificate data and patient discharge data. Outcomes were mode of delivery (among laboured deliveries) and select regional anaesthesia complications. Multivariable Poisson regression was used to adjust for maternal characteristics. Results: In women undergoing labour (i.e. laboured delivery), women with higher BMI categories were more likely to receive regional analgesia in a dose–response fashion (adjusted risk ratio [RR] 1.10, 95% confidence interval [CI] 1.10, 1.11 for primiparous women with category I obesity), and in those receiving regional anaesthesia, were less likely to deliver vaginally (e.g. RR 0.85, 95% CI 0.84, 0.85 for the same category of women). Regional anaesthesia complications displayed a complex relationship with maternal BMI, with women in intermediate obesity categories having decreased odds as compared to normal-weight women, and women in the highest BMI category having a twofold increased risk of complications (RR 2.34, 95% CI 1.37, 4.02 for primiparous women). Conclusion: Labouring women in higher BMI categories were more likely to receive regional anaesthesia and more likely to deliver via caesarean compared to normal weight women and women without regional anaesthesia. Rates of anaesthesia complications were highest among women in the highest BMI category.