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Placenta-Grading
Submitted by Tara Herzberg, MD

 

  • Vascularity
    • Very vascular – has 2 blood supplies
      • Blood from fetus through 2 (sometimes 1) umbilical arteries through umbilical cord from fetal hypogastric arteries to placenta
      • 1 umbilical vein carries blood back to fetal left portal vein
      • Blood from mom through branches of uterine arteries through the myometrium (arcuate arteries) through the basilar plate (spiral arteries) into the placenta
  • The two circulations intertwine in the placenta but do not mix
    • Exchange of oxygen and nutrients occurs over the large vascular surface area
    • Maternal venous channels in the placenta are hypoechoic or anechoic spaces called venous lakes (usually small, but can be large)
  • Anatomy on US
    • Inner border of placenta against the uterine wall has the combined hypoechoic myometrium and interposed basilar layer = hypoechoic band called the decidua basalis (contains maternal blood vessels)
    • Outer surface abutting the amniotic fluid = chorionic plate (chorioamniotic membrane) = bright specular reflector
  • Placental thickness judged subjectively
    • But if measure at midposition or cord insertion 2-4 cm = normal

Grade 0

  • Late 1st trimester-early 2nd trimester

  • Uniform moderate echogenicity

  • Smooth chorionic plate without indentations

 

 

Grade 1

  • Mid 2nd trimester –early 3rd trimester (~18-29 wks)

  • Subtle indentations of chorionic plate

  • Small, diffuse calcifications (hyperechoic) randomly dispersed in placenta

Grade 2

  • Late 3rd trimester (~30 wks to delivery)

  • Larger indentations along chorionic plate

  • Larger calcifications in a “dot-dash” configuration along the basilar plate

Grade 3

  • 39 wks – post dates

  • Complete indentations of chorionic plate through to the basilar plate creating “cotyledons” (portions of placenta separated by the indentations)

  • More irregular calcifications with significant shadowing

  • May signify placental dysmaturity which can cause IUGR

  • Associated with smoking, chronic hypertension, SLE, diabetes

Rumack
The Requisites-GU Radiology

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