Three-Dimensional Power Doppler Ultrasonography for Diagnosing Abnormally Invasive Placenta and Quantifying the Risk.

OBJECTIVE To test an objective ultrasound marker for diagnosing the presence and severity of abnormally invasive placenta. METHODS Women at risk of abnormally invasive placenta underwent a three-dimensional power Doppler ultrasound scan. The volumes were examined offline by a blinded observer. The largest area of confluent three-dimensional power Doppler signal (Area of Confluence [Acon], cm) at the uteroplacental interface was measured and compared in women subsequently diagnosed with abnormally invasive placenta and women in a control group who did not have abnormally invasive placenta. Receiver operating characteristic curves were plotted for prediction of abnormally invasive placenta and abnormally invasive placenta requiring cesarean hysterectomy. RESULTS Ninety-three women were recruited. Results were available for 89. Abnormally invasive placenta was clinically diagnosed in 42 women; 36 required hysterectomy and had abnormally invasive placenta confirmed histopathologically. Median and interquartile range for Acon was greater for abnormally invasive placenta (44.2 [31.4-61.7] cm) compared with women in the control group (4.5 cm [2.9-6.6], P<.001) and even greater in the 36 requiring hysterectomy (46.6 cm [37.2-72.6], P<.001). Acon rose with histopathologic diagnosis: focal accreta (32.2 cm [17.2-57.3]), accreta (59.6 cm [40.1-89.9]), and percreta (46.6 cm [37.5-71.5]; P<.001 analysis of variance for linear trend). Receiver operating characteristic analysis for prediction of abnormally invasive placenta revealed that with an Acon of 12.4 cm or greater, 100% sensitivity (95% confidence interval [CI] 91.6-100) could be obtained with 92% specificity (95% CI 79.6-97.6); area under the curve is 0.99 (95% CI 0.94-1.0). For prediction of abnormally invasive placenta requiring hysterectomy, 100% sensitivity (95% CI 90.3-100) can be obtained with an Acon of 17.4 cm or greater with 87% specificity (95% CI 74.7-94.5; area under the curve 0.98 [0.93-1.0]). CONCLUSION The marker Acon provides a quantitative means for diagnosing abnormally invasive placenta and assessing severity. If further validated, subjectivity could be eliminated from the diagnosis of abnormally invasive placenta. LEVEL OF EVIDENCE II.