Placenta Previa is an obstetric complication that classically presents as painless vaginal bleeding in the third trimester secondary to an abnormal placentation near or covering the internal cervical os. However, with the technologic advances in ultrasonography, the diagnosis of placenta previa is commonly made earlier in pregnancy. Historically, there have been three defined types of placenta previa: complete, partial, and marginal. More recently, these definitions have been consolidated into two definitions: complete and marginal previa.
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