Model discrimination
Among the entire cohort, a logistic regression model was fit using the final selected variables to predict maternal acute end-organ injury or death from 20 weeks’ gestation until 42 days postpartum. A backward elimination method was applied for variable selection, with predictor evaluation based on a balance of the model’s C-statistic, clinical influence, and statistical significance. For continuous predictor variables such as age in which non-linear associations with the outcome were observed, a quadratic (squared) term was added to the model. Model discrimination was expressed as a C-statistic and its 95% CI, as well as visual detection of a receiver operating curve (ROC). We considered a C-statistic of < 0.5 to be not useful, 0.5 to 0.6 poor, 0.6 to 0.7 moderate, and ≥ 0.7 as good.25