Jamie Lynn Lipo -- Big, Fat Lies

Sources tell TMZ Jamie Lynn Spears is swelling up with anger over one gossip mag's claims she had lipo while pregnant -- so much so that she may take legal action.

We're told the story is "100% NOT true" -- that Jamie Lynn has never had lipo and would "never in her life" do anything like it.

Calls to Jamie Lynn's publicist have not been returned.