News | Why does placenta accreta occur? UCLA offers an explanation
A UCLA Health-led study suggests that placenta accreta spectrum (PAS) is driven not by abnormal placental growth itself, but by disorganized collagen as a previous cesarean scar heals, disrupting the normal barrier between placenta and uterus.
Once considered rare, PAS now affects about 14,000 pregnancies annually and is a major cause of severe postpartum hemorrhage and maternal death. The placenta invades too deeply into the uterine wall and cannot detach normally after delivery, often requiring hysterectomy.
Previous cesarean delivery is the strongest and most common PAS risk factor, but the biological mechanism has long been unclear. The UCLA Health study provides an important clue.
"The real problem in placenta accreta is not the placenta, but how uterine scar tissue heals," said corresponding author Yalda Afshar, associate professor of maternal-fetal medicine at the UCLA David Geffen School of Medicine and co-director of the UCLA Health Placenta Accreta Spectrum Care Program. "The scar changes the structure and organization of collagen in the uterus, significantly increasing delivery risks."
Published in the American Journal of Obstetrics and Gynecology, the study combined human surgical specimens, mouse models, and a laboratory "placenta accreta model." Advanced three-dimensional imaging showed tangled, disorganized collagen fibers at previous uterine scars, weakening the tissue boundary and creating conditions for abnormal placental attachment and invasion.
The team studied tissue from 13 patients with PAS and 10 at-risk patients without PAS, sampling placental attachment and nonattachment sites. Persistent inflammation and macrophages disrupted normal scar remodeling, leading to abnormal collagen and promoting placental attachment.
Not all cesarean scars heal in the same way, which may explain why PAS develops in some women with previous cesareans but not others.
Afshar said assessing scar healing and collagen structure before pregnancy or early in pregnancy might eventually identify high-risk patients and improve perinatal care and outcomes.
The mechanism also lays groundwork for new imaging, biomarkers, or interventions that could reduce maternal and infant risks as cesarean rates remain high.
News | Why does placenta accreta occur? UCLA offers an explanation
News | Why does placenta accreta occur? UCLA offers an explanation
A UCLA Health-led study suggests that placenta accreta spectrum (PAS) is driven not by abnormal placental growth itself, but by disorganized collagen as a previous cesarean scar heals, disrupting the normal barrier between placenta and uterus.
Once considered rare, PAS now affects about 14,000 pregnancies annually and is a major cause of severe postpartum hemorrhage and maternal death. The placenta invades too deeply into the uterine wall and cannot detach normally after delivery, often requiring hysterectomy.
Previous cesarean delivery is the strongest and most common PAS risk factor, but the biological mechanism has long been unclear. The UCLA Health study provides an important clue.
"The real problem in placenta accreta is not the placenta, but how uterine scar tissue heals," said corresponding author Yalda Afshar, associate professor of maternal-fetal medicine at the UCLA David Geffen School of Medicine and co-director of the UCLA Health Placenta Accreta Spectrum Care Program. "The scar changes the structure and organization of collagen in the uterus, significantly increasing delivery risks."
Published in the American Journal of Obstetrics and Gynecology, the study combined human surgical specimens, mouse models, and a laboratory "placenta accreta model." Advanced three-dimensional imaging showed tangled, disorganized collagen fibers at previous uterine scars, weakening the tissue boundary and creating conditions for abnormal placental attachment and invasion.
The team studied tissue from 13 patients with PAS and 10 at-risk patients without PAS, sampling placental attachment and nonattachment sites. Persistent inflammation and macrophages disrupted normal scar remodeling, leading to abnormal collagen and promoting placental attachment.
Not all cesarean scars heal in the same way, which may explain why PAS develops in some women with previous cesareans but not others.
Afshar said assessing scar healing and collagen structure before pregnancy or early in pregnancy might eventually identify high-risk patients and improve perinatal care and outcomes.
The mechanism also lays groundwork for new imaging, biomarkers, or interventions that could reduce maternal and infant risks as cesarean rates remain high.
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