Diagnostic accuracy of ultrasound in detecting the depth of invasion in women at risk of abnormally invasive placenta: A prospective longitudinal study

Introduction: The aim of this study was to assess the diagnostic accuracy of ultrasound in detecting the depth of abnormally invasive placenta in women at risk. Material and methods: Prospective longitudinal study including women with placenta previa and at least one prior cesarean delivery or uterine surgery. Depth of abnormally invasive placenta was defined as the degree of trophoblastic invasion through the myometrium and was assessed with histopathological analysis. The ultrasound signs explored were: loss of clear zone, placental lacunae, bladder wall interruption, uterovesical hypervascularity, and increased vascularity in the parametrial region. Results: In all, 210 women were included in the analysis. When using at least one sign, ultrasound had an overall sensitivity of 100% (95% CI 96.5-100) and overall specificity of 61.9 (95% CI 51.9-71.2) for all types of abnormally invasive placenta. Using two ultrasound signs increased the diagnostic accuracy in terms of specificity (100%, 95% CI 96.5-100) but did not affect sensitivity. When stratifying the analysis according to the depth of placental invasion, using at least one sign had a sensitivity of 100% (95% CI 93.7-100) and 100% (95% CI 92.6-100) for placenta accreta/increta and percreta, respectively. Using three ultrasound signs improved the detection rate for placenta percreta with a sensitivity of 100% (95% CI 92.6-100) and a specificity of 77.2% (95% CI 69.9-83.4). Conclusion: Ultrasound has a high diagnostic accuracy in detecting the depth of placental invasion when applied to a population with specific risk factors for anomalies such as placenta previa and prior cesarean delivery or uterine surgery. © 2018 Nordic Federation of Societies of Obstetrics and Gynecology