Objectives:  To examine the usefulness of sonographic criteria in the assessment of the lateral extent and depth of myometrial involvement in morbidly adherent placenta.

Methods:  From hospital records and a perinatal database, women with morbidly adherent placenta confirmed at delivery and antenatal ultrasound assessment in 2004–2007 were identified. The sonographic appearance at the time of antenatal assessment was compared with the clinical and histological findings at delivery. Following statistical analysis, useful sonographic features in the assessment of myometrial invasion were identified.

Results:  Nine cases, including one case of placenta percreta, eight cases of accreta or increta of which one minor partial, were reviewed. The criteria useful for the assessment of the lateral placental/myometrial involvement were obliteration of retroplacental clear space, increased subplacental vascularity, placental‐tissue interface disruption and vessels crossing the interface disruption site with the last 2 signs applicable for helpful for assessment of the parametrium; and for the assessment of the depth, bladder serosa–uterine wall interface hypervascularity, vessels extending from placenta to bladder, placental‐tissue interface disruption and vessels crossing placental‐tissue interface disruption. The myometrial vascular pattern was also helpful in assessing the extensiveness of myometrial involvement. There was bulging of the lower uterine wall in the case of placenta percreta.

Conclusions:  Assessment of the placental/myometrial involvement of morbidly adherent placenta is possible on antenatal ultrasound examination. Combinations of different criteria may be required in assessing the lateral extent and the depth of placental/myometrial involvement.