Welcome in H.C.M. for consulting.
I have gone through your query regarding small cystic lump in throat behind the uvula
. I suspect that you are having Antrochoanal Polyp. This polyp arises from maxillary sinus
and passes through nasal cavity
to throat where it hangs behind the uvula. Since you are pregnant so to avoid hazards of radiation
of x-ray I would like to suggest you to consult an E.N.T.specialist for examination of nose and throat to find out the reality of this cystic lesion.