TABLE 3.

Pooled area under the receiver operating characteristic curves (AUCs) for gestational age at ultrasound (Base) compared to that with addition of low fetal heart rate and small crown–rump length (Primary), Primary compared to that with addition of maternal age (Age) or systolic and diastolic blood pressures (Blood pressure) or yolk sac diameter and subchorionic Hemorrhage (YSD + hemorrhage) or continuous expression of fetal heart rate and crown–rump length (Continuous) using 25% test sets

ROC association statistics	Mann–Whitney
ROC model	Area (95% CI)
Base	0.630 (0.471, 0.788)a
Primary	0.775 (0.653, 0.898)
Age	0.785 (0.662, 0.909)
Blood pressure	0.804 (0.702, 0.905)
YSD + hemorrhage	0.774 (0.646, 0.902)
Continuous	0.794 (0.665, 0.923)
ROC contrast estimation	Difference in area (95% CI)
Primary − Base	0.146 (0.00206, 0.294)
Age − Primary	0.00993 (−0.0145, 0.0346)
Blood pressure − Primary	0.0282 (−0.0321, 0.0885)
YSD + hemorrhage − Primary	−0.00145 (−0.271, 0.0242)
Continuous − Primary	0.0185 (−0.0419, 0.0798)

The area under the receiver operating characterisic curve (AUC) for each model is provided in ROC association statistics. Differences in area between models are provided in ROC contrast estimation. The increase in area under the AUC after adding fetal heart rate and crown–rump length is substantively improved, although not significantly, as shown by the ROC contrast estimation of a confidence interval (CI) that includes 0. There are no statistically significant or substantive differences in AUC with either addition of maternal age or blood pressure, or yolk sac diameter and subchorionic hemorrhage, or by continuous expression of fetal heart rate and crown–rump length.

^aAll 10 imputations expectedly had identical estimates of 0.630 (0.471, 0.788), due to the absence of missingness for gestational age and clinical loss.