Early diagnoses of placental problems including placenta previa and placenta accreta are helpful with outcomes for mothers and babies.  Placenta previa and accreta are in fact low lying or infiltrating.  They are more common after a previous caesarean section or procedures such as IVF.  The RCOG has renewed its guidelines in a view to improving early diagnosis of this condition at the 20 week ultrasound so that management can be planned to optimise outcomes.