9mm paraovarian cyst appeared after pregnancy- was not seen before pregnancy. not a follicle. can they grow during pregnancy? why wasn't there before?

Definitely can grow: Paraovarian or tubal cysts can definitely grow during pregnancy. You wrote 9mm, but did you mean 9cm? A 9mm cyst is pretty small and i would be surprised that your doctor even commented when so small. Typically these cysts are filled with water. We don't know why they form, inflammation? Regardless, when filled with water, they almost always resolve. Unless 9cm... Which means maybe surgery.