Fig. 4

ROC curve, Calibration curve and decision curve of the predicting model in the validation set. a–c Showed the ROC curve, calibration curve and decision curve. The calibration curve examined the agreement between the observed and predicted probabilities. The x-axis of the calibration curve demonstrates the nomogram-predicted probability, while the y-axis demonstrated the observed probability. A 45° diagonal line showing ideal calibration performance, where the observed probability strictly equals the predicted probability. The slope and Brier score quantify the approaching degree of actual line to the ideal diagonal line, with the scope approaching 1.000 and the Brier score approaching 0.000 showing good calibration ability. The decision curve evaluated the clinical utility of the nomogram, with the vertical axis showing standardized net benefit and the horizontal axis showing high risk threshold. The solid black line represents the net benefit when all patients are considered not to develop the outcome (Intrauterine pregnancy). The solid grey line represents the net benefit when all patients are considered to develop the outcome (Ectopic pregnancy).