Statistical analyses
hypotension
Continuous and categorical variables were summarized as mean ± standard deviation (SD) or median (interquartile range (IQR) [range]) as appropriate, or number (proportion) respectively. Categorical and continuous variables were compared using the XA sample size of 92 parturients (46 in each group) is required to detect 25.5% absolute difference in the incidence of hypotension, based on the following assumptions: incidence of hypotension in ADIVA group of 13.5%, incidence of hypotension in DIVA group of 39.0% based on previous DIVA studies on reported incidence and difference in incidence [