Flixonase is the trade name; the name of the medicine is fluticasone - a steroid. Steroids taken for local nasal use are not prohibited in pregnancy, though one should not use any medicine for prolonged therapy including steroids.
For allergic rhinitis, there are quite a few non-steroidal medicines such as levocabastine (Trade name: Livostin), azelastine (Trade name: Rhinolast), ipratropium (Trade name: Rinatec), sodium cromoglycate (Trade name: Rynacrom; used for prevention rather than acute attack).
Trade names can differ from country to country.