Large subserosal fibroid seen in fundal region (11.78*11.02*9.00 CM) vol 612 ml please suggest best treatment and how harmful it is?

Symptoms or not? If you are having symptoms then there are surgical, and other methods for removing or reducing the fibroid. If you are not having symptoms, and at your age of 29 then monitoring the growth is an option with more frequent GYN MD visits, especially if you have not yet been pregnant. Talk to your MD to discuss many options which are based on the above scenarios.