9.9cm Ovary Cyst In 3rd Trimester

Hi, Have anyone experienced a cyst only being identified on the 3rd trimester? Also did you go for normal birth after that? Or you had to remove it? Or what actually You did. I’m pretty confused as I went for a dermoid cyst removal in 2019. And I’m currently pregnant 28weeks. Today’s scan showed a 9.9cm Cyst on the right ovary. Dr couldn’t answer how come all along they didn’t identify that. So I’m puzzled. Also I had a normal delivery 8years ago. So I’m not keen on doing a c-sect. Kindly share your review.