Placenta Previa: Classification, Risks, and Delivery Planning

Placenta previa = placental tissue covering internal cervical os.

Classification

• Complete: covers os entirely.
• Partial: covers part.
• Marginal: edge at os.
• Low-lying: <2 cm from os (not previa).

Risks

• Painless bright red bleeding (2nd/3rd trimester).
• Preterm birth, PPH, placenta accreta spectrum (if prior uterine surgery).
• Fetal: growth restriction, malpresentation.

Management

• Expectant: <34 wks, minimal bleeding → corticosteroids, tocolytics, hospitalization, avoidance of vaginal exam/intercourse.
• Delivery: 36–37 weeks (complete/partial); 37–38 weeks (marginal/low-lying) via cesarean (only safe route for complete/partial).
• Emergency cesarean for life-threatening hemorrhage.

Risk Factors

Prior cesarean, curettage, IVF, advanced maternal age, multiparity, smoking, cocaine.