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Figures
Figure 1: Identification of studies of uterine artery Doppler ultrasonography used to predict pre-eclampsia and intrauterine growth restriction, for inclusion in the meta-analysis. *Includes 6 studies on pre-eclampsia and 8 on intrauterine growth restriction that were added after manual search of bibliographies of selected articles.
Figure 2: Plots of receiver operating characteristics showing pooled and single accuracy estimates, with 95% confidence intervals, for uterine artery Doppler indices to predict pre-eclampsia and intrauterine growth restriction in the second trimester according to patient risk. Note: the x axis shows reversed specificity. The closer the index values are to the upper left corner of each graph, the greater the accuracy of that index. The test index that best predicted the development of pre-eclampsia (highest positive likelihood ratio) in low-and high-risk patients was an increased pulsatility index with notching. This index was also the best predictor of intrauterine growth restriction in low-risk patients. For intrauterine growth restriction in high-risk patients, the Doppler indices showed low predictive value. (The thresholds for the Doppler indices reported in the studies we reviewed are provided in Appendices 3 and 4 [available online at www.cmaj.ca/cgi/content/full/178/6/701/DC2].)
Figure 3: Plots of receiver operating characteristics showing pooled and single accuracy estimates, with 95% confidence intervals, for uterine artery Doppler indices to predict severe pre-eclampsia and severe intrauterine growth restriction in the first and second trimester. Note: the x axis shows reversed specificity. The closer the index values are to the upper left corner of each graph, the greater the accuracy of that index. In low-risk patients, an increased pulsatility index was the test characteristic that best predicted the development of severe pre-eclampsia or severe intrauterine growth restriction (highest positive likelihood ratio). In high-risk patients, the best predictor of each outcome was an increased resistance index > 0.58. (The thresholds for the Doppler indices reported in the studies we reviewed are provided in Appendices 3 and 4 [available online at www.cmaj.ca/cgi/content/full/178/6/701/DC2].)