Placenta Previa

Placenta previa involves ectopic implantation in the lower uterine segment where the decidua basalis is thinner and less vascularized than the fundal region. This results in abnormal trophoblastic invasion and a higher rate of placenta accreta spectrum disorders (accreta, increta, percreta), particularly in patients with prior uterine scars. The lower segment's limited contractile ability after placental separation contributes to hemorrhage that is unresponsive to uterotonics alone. The clinician must integrate diagnostic imaging, classify the previa, manage expectant versus active management protocols, prescribe corticosteroids for fetal lung maturity, order blood products, and determine delivery timing in consultation with maternal-fetal medicine.