29 Placenta Previa

Placenta previa

Placenta Previa is divided into four grades depending on the relationship and distance to the internal cervical os:

  • grade I: low-lying placenta: placenta lies in the lower uterine segment but its lower edge does not abut the internal cervical os (i.e lower edge 0.5-2.0 cm from internal os).
  • grade II: marginal previa: placental tissue reaches the margin of the internal cervical os, but does not cover it
  • grade III: partial previa: placenta partially covers the internal cervical os
  • grade IV: complete previa: placenta completely covers the internal cervical os

Sometimes grades I and II are termed a “minor” or “partial” placenta previa, and grades III and IV are termed a “major” placenta previa.