At my 20 week ultra sound a cyst was found on the umblical cord. It was small about 1 centimeter. I was freaked out but the doctor said it was nothing to worry about and was having no effect on the baby. I had to do another ultra sound a month later just to check on it, and it had completly dissolved.
I was so releived. so from everything I have read the cysts usually pose no problems with the baby or pregnancy, and the usually dissolve on their own.