Placenta Accreta Spectrum (PAS) disorders encompass various degrees of pathologic placental implantation and are classified on the basis of the depth of myometrial invasion.
Placenta accreta is the mildest and most common among the PAS disorders wherein villi only attach to the myometrium without invasion of the underlying muscle. Placenta increta is the intermediate form with partial invasion of the myometrium. The most severe form is placenta percreta where the villi penetrate through the entire myometrium or even beyond the serosa into adjacent organs.
The leading hypothesis is that PAS is due to the deficiency of the endometrial-myometrial interface leading to failure of normal decidualization, often in the area of a uterine scar, which allows deep chorionic villi and trophoblast infiltration. PAS disorders have increased in parallel with the increased rates of cesarean section and placenta previa, its most significant risk factors. Global cesarean section rates are predicted to be around 40-60% by 2030[1]. The incidence of PAS has increased nearly ten times in the last five decades and represents a significant contributor to maternal health complications and deaths due to massive obstetric hemorrhage with around 52% necessitating peripartum hysterectomy [2].
Ultrasound remains the first-line imaging modality in assessment of PAS. Recently, MRI has been increasingly utilized for diagnosis and pre-surgical evaluation of myoinvasion and extrauterine spread. Standardizing imaging criteria is crucial for consistent reporting and diagnosis, ultimately guiding timely and tailored clinical interventions for improved patient outcomes.