We were diagnosed with a CPC at 18.5 weeks with DS1, went in for a 2nd level ultrasound at 23 weeks and it was gone. Fast forward to this pregnancy, i went in for my A/S at 18.5 weeks and we were all good, went in to an sonography class because they needed a pt at 22 weeks and they found one. I go in to the specialist again next week, just to make sure all is in the clear.
From my experience they cause more worry to the parents than anything, the dr's all blow it off like it's no big deal! Stay positive and try not to worry!