"Marginal" placenta?

July 14, 2011
Joe Antony, MD
Joe Antony, MD

Sending you an image of placenta, in late pregnancy (3rd trimester). I think it is low lying. Question is: can it be called mild previa?

5/27/99
Hello netfriend,
Sending you an image of placenta, in late pregnancy (3rd trimester). I think it is low lying. Question is: can it be called mild previa? Do you grade pl. previa sonographically? If so, how? Do reply at: jscan@vsnl.com
Regards, DR. JOE ANTONY, COCHIN, INDIA

Comments:

Dr. Antony,
This placenta appears to be a "Marginal" placenta because it touches the internal os. However, because the bladder is so full, anterior placentas like this can be misleading if the bladder pushes the placenta down to touch the posterior wall. A bit of bladder emptying might make the effect look clearer.

There are basically four kinds of placenta in relationship to the birth canal...

  • "low lying placenta", but not touching the os
  • "marginal placental previa", like this one appears. Touching the birth canal but not clearly crossing the os.
  • "partial previa" with a small portion crossing the os.
  • "complete previa" in which the previa is clearly implanted over the os... these are unlikely to move or "migrate".

All of these may "migrate" in the last half of the pregnancy.

My main concern with this particular placenta is the apparent loss of the "subplacental vascular complex" just cephalic to your label "placenta" ... there is some chance that this could represent placenta accreta. The bladder wall echoes seem to thin in this area also. Do you know if this woman has had a prior C-section or other surgical interventions that might have scarred her endometrium?

Terry DuBose