Significance of free fluid in the pelvic cul de sac

My mom was first diagnosed with stage II Ovarian Cancer 8 years ago, at the age of 53, had a recurrence 4 years ago and is now in remission.  I am 32, have three children ages 11, 9 and 3 and no significant medical history.  Today, during a routine exam and sono, my doctor saw moderate to large amounts of free fluid in the pelvic cul de sac, ( I now realize the source of the bloating and pressure I've been feeling ). I've also been having some persistent low grade fever (99.5/6) that's not associated with being sick. He wants an MRI done immediately, a blood test for the cancer markers and some further tests.  He feels it may be a multitude of other things, but because of the family history feels concerned and mentioned ovarian cancer as one of the possibilities.  I am certainly going to follow through with all of his recommendations, but meanwhile I can not help feeling absolutely lost.  Can someone shed light on the significance of and link between the fluid and ovarian cancer and the likelihood that it is or isn't?

[Kimchi]

I know about ascites in the abdomen cavity but from what I understand from a little researche it's not the same as free fluid in the pelvic cul de sac (Pouch of Douglas).  But I did see something about ascites leaking int pelvic cul de sac .