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First off, blood tests just means getting blood drawn from your arm. No big deal.
The TB test, though, I would call your OB about, just to make sure it's ok. Your doctor may want you to forgo testing unless you are working in a high risk setting (where getting TB would be worse than any potential side effects from the testing itself).
There is a lot of info out there on the web if you do a search for it. I would specifically look to the CDC's and FDA's recommendations.