Thought I had read just about everything on pregnancy

I'm on baby number 4, and with each of my other 3 I of course went and read tons and tons of material on pregnancy and possible complications, what's normal etc. I thought I had read just about everything.

Now looking over my ultrasound report I see a term I never came across before, Velamentous insertion. Of course there's no explanation on the report, it's intended to be seen by the doctors, not the patients. So I looked it up, and it is when the umbilical cord attaches at the edge of the placenta instead of the middle and some of the blood vessels are not within the amniotic sac and are not protected by the jelly like substance in the umbilical cord.

Just when you think you've read it all, there's more to learn!

(Note my u/s was unclear if I have this going on, they are doing another in a few days to determine if it is actually velamentous or just marginal where the vessels are still protected, but attached near the edge of the placenta)