Placenta accreta spectrum (PAS) is a pregnancy complication that now affects about 14,000 pregnancies each year in the United States. The condition, which was once considered rare, is now recognized as a significant cause of maternal death. In PAS, the placenta attaches too deeply into the uterine wall and fails to detach after childbirth, often resulting in severe bleeding and sometimes requiring a hysterectomy.
A leading risk factor for PAS is having had a previous cesarean delivery. Scarring from earlier cesarean births can alter how the placenta attaches in subsequent pregnancies. Researchers at UCLA Health have conducted new research suggesting that the healing process of this scar tissue may be central to understanding how PAS develops and why some women are at higher risk.
"Our findings show that the main problem in placenta accreta isn't the placenta growing abnormally - it's how uterine scarring changes the structure and organization of collagen in the uterus to increase delivery risks," said Yalda Afshar, MD, associate professor of obstetrics and gynecology in the division of maternal fetal medicine at the David Geffen School of Medicine at UCLA, co-director of the UCLA Health Accreta Care Program and corresponding author of the study.
The study appeared in the American Journal of Obstetrics and Gynecology. It utilized surgical specimens from patients, mouse models, and a laboratory-grown "accreta-in-a-dish" system to investigate collagen structures within uterine scars. Through advanced 3D imaging techniques, researchers observed that tangled or irregular collagen at old uterine scars disrupts the normal boundary between uterus and placenta. This disruption creates an environment where abnormal placental attachment can occur, increasing delivery risks.
Samples were collected from 13 patients diagnosed with PAS and 10 patients who had risk factors but did not develop PAS. Tissue was taken both from areas where the placenta adhered to scar tissue and where it did not. The research found that ongoing inflammation and immune cells known as macrophages interfere with normal remodeling of scars. This leads to abnormal collagen architecture that facilitates improper placental attachment.
