Placental grading

Last revised by Dr Jeremy Jones on 20 Sep 2021

Placental grading (Grannum classification) refers to an ultrasound grading system of the placenta based on its maturity. This primarily affects the extent of calcifications. In some countries, the use of placental grading has fallen out of obstetric practice due to a weak correlation with adverse perinatal outcome 5.

Mismatched grades for gestational age are considered abnormal. Grading is however still based on visual appearance of the placenta.

The grading system is as follows:

  • grade 0: <18 weeks
  • grade I: 18-29 weeks
    • occasional parenchymal calcification/hyperechoic areas
    • subtle indentations of chorionic plate
  • grade II: ​30-38 weeks
    • occasional basal calcification/hyperechoic areas
    • deeper indentations of the chorionic plate (does not reach up to the basal plate)
      • seen as comma type densities at the chorionic plate
  • grade III: ​​≥ 39 weeks
    • significant basal plate calcification
    • chorionic plate interrupted by indentations (frequently calcified) that reach up to the basal plate: cotyledons
    • an early progression to a grade III placenta is concerning and is termed as hyper mature placenta and sometimes associated with placental insufficiency
      • associated with smoking, chronic hypertension, SLE, diabetes.

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