Lecture: Placental Grading in ultrasound. 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 View Picture

• Late 1^st trimester-early 2^nd trimester

• Uniform moderate echogenicity

• Smooth chorionic plate without indentations.

Grade 1 View Image

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

• Subtle indentations of chorionic plate

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

Grade 2 View Picture

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

• Larger indentations along chorionic plate

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

Grade 3 View Picture

• 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