drypantz, sometimes during pregnancy, there's this cyst known as corpus luteum, and it secretes progesterone to maintain the pregnancy. This function of producing progesterone is gradually taken over by the placenta. the corpus leuteum then disintegrates and disappear.
I had a cyct on my right ovary too, detected during the 6-7 weeks scan, then at the next scan on week 12, the cyst is gone.
If yours is a corpus leuteum too, it will probably disappear by the next scan.
If it isn't, and the cyst is not giving u problem eg pain or growing bigger and bigger, i think doctors will normally leave it alone and monitor. if u plan to do a c-sect, then can remove at the same time. if not, if u decide to remove it after delivery, then have to be a seperate op.
Anyway I think u don't need to worry about it, i asked my gynae before as well, the cyst will not affect the preganancy/baby at all..