Placenta accreta spectrum (PAS), once considered a rare obstetric condition, now affects an estimated 14,000 pregnancies each year and represents a significant cause of maternal morbidity and mortality. Despite its increasing incidence, the underlying mechanisms driving PAS remain incompletely understood. PAS occurs when the placenta abnormally invades the uterine wall and fails to separate after delivery, often resulting in severe hemorrhage and the need for hysterectomy.
Prior cesarean delivery is the most significant and prevalent risk factor for PAS. Scar formation following cesarean birth alters the uterine environment, influencing placental attachment in subsequent pregnancies. Recent research led by UCLA Health suggests that aberrant healing of uterine scar tissue may play a central role in PAS development, risk stratification, and abnormal placental invasion.
“Our data indicate that placenta accreta is not primarily a disorder of placental overgrowth, but rather a consequence of altered collagen organization within uterine scar tissue,” said Yalda Afshar, MD, associate professor of obstetrics and gynecology at the David Geffen School of Medicine at UCLA and corresponding author of the study.
Published in the American Journal of Obstetrics and Gynecology, the study integrated analysis of surgical specimens, a mouse model, and a novel in vitro “accreta-in-a-dish” system. Using advanced three-dimensional imaging, investigators demonstrated that disorganized collagen at prior uterine scars disrupts the normal boundary between the placenta and myometrium, creating a permissive environment for abnormal placental attachment and high-risk delivery outcomes.
Analysis of tissue samples from 13 patients with PAS and 10 control patients with risk factors but no PAS revealed persistent inflammation and macrophage infiltration at scar sites. These immune processes impaired normal scar remodeling, resulting in abnormal collagen architecture that facilitates pathological placental adherence.
