From: Collins SL, Ashcroft A, Braun T, Calda P, Langhoff-Roos J, Morel O, et al. Proposal for standardized ultrasound descriptors of abnormally invasive placenta (AIP). Ultrasound Obstet Gynecol. 2016;47(3):271-5.
This sign is extremely subjective and can be extremely difficult to interpret as normal placentae can look excessively vascular. As the placental bed is rarely examined during routine ultrasound scans it can appear 'hypervascular' the first time the colour Doppler is turned on. Consequently this sign must be interpreted with significant caution unless the operator is highly experienced with ultrasound imaging of PAS. This may explain why this was one of the signs frequently seen in normal placentae in the study by Philips et al.