Can tattoos affect epidurals? I was told that some doctors will not give an epidural if the patient has a back tattoo, is this true?

Fear. Some doctors fear that the ink can get in the spinal canal or fluid...
No. There is a fear that any scarring would mar the tattoo (especially in people most likely to form keloid scars). Some have expressed concern that the ink would be pushed into the spinal area but this has not proved to be any problem.
Possibly. Research is very limited. Unless a tattoo is recent and still healing, red, swollen or oozing, an anesthesia provider will try to insert the needle through an open area in the tattoo design. Every attempt should be made to avoid trapping pigment and moving it further into your tissues. Discuss with your provider. Something to your satisfaction can be worked out.
I . I can't say that I have ever denied an epidural for a tattooed lower back, nor have i heard of any colleagues who would flatly deny an epidural in this situation. In fact, if a patient has anatomy that i can feel then sometimes the tattoo gives me a visible reference point for the procedure, and could be helpful. But i really do mean sometimes. What could become an issue is a large tattoo that obscures the anatomical landmarks which help the anesthesiologist find the way to the epidural space. However, a fresh tattoo is necessarily a violation of the skin, and the tattoo needle will carry bacteria down under the skin. If there were a freshly placed, unhealed tattoo over the lower back, i would not offer an epidural for the risk of carrying that bacterial contamination down to the epidural space, which could lead to abscess or meningitis. These are very serious problems and are only some of many reasons not to get a new tattoo while pregnant.