Do you have a follow up appt with your OB?
From what i can tell its a peri-sac haemotoma and noramlly has no effect on the developing foetus, but Im just googling.

Alan might have a better idea than me.

When you feel up to it, call the u/s place (or have your care providcer do it) and make a complaint becuase thats just not for them on to scare the crap out of someone!