Odds of oophorectomy with ovarian cyst?

Dear Ask The Doctor: I am a 30 year old female found to have a left ovarian cyst approximately one year ago. My gyn monitored it, and it kept growing, and now it is to the point where it needs to be removed because of the size and the potential to twist the ovary. Initially I had a few sharp pains when it was discovered. However, now I don't have much pain. Just a few twinges here and there. I believe it be around 6-7cm, and she described it as most likely a blood filled endometrioma. I am going to undergo a laparoscopy in hopes she can drain or remove it. However, I may need to have the ovary removed if this is unsuccessful. I am worried about losing an ovary, even though the other will compensate. Is there anyway you can give me a rough estimate, generally speaking, of how often the ovary actually needs to be removed with these types of ovarian cysts? Thank you!

Dear Tina: Unfortunately, there is no way to determine if your ovary will have to be removed to effectively treat the cyst. This decision can only be made after the surgeon examines the cyst at the time of the operation. Every effort will be made to avoid removing the ovary.