Pathophysiology
Clinical meaning
Placenta previa occurs when the placenta abnormally implants over or near the internal cervical os. As the cervix dilates and effaces during pregnancy or labor, placental blood vessels are disrupted, causing painless vaginal bleeding that can progress to massive hemorrhage. The placenta may partially or completely cover the os. As pregnancy advances, the placenta may migrate away from the cervical opening, potentially resolving the previa. The nurse monitors maternal vital signs, bleeding patterns, and fetal heart rate, reporting all changes to the nursing team immediately.