Ovarian cyst

I was told at my 7 weeks confirmation scan that I have a 6cm cyst on my left ovary. The doctor said it would most likely go away on its own by the second trimester but I just had my 20 week anatomy scan and it is still there and around the same size. She said it looks just like a simple fluid filled cyst but of course I’m still worried. Has anyone had this happen? Did it end up resolving or did you have to get it removed?