There is NO TRUTH to the urban legend that you can not get an epidural (spinal) administered if the needle would have to pass through a tattoo!
Some misguided doctors have refused to perform epidurals on women with tattoos that the needle would have to pass through (ie. between the second and third lumbar vertebrae). The reason for the worry is the risk of the needle passing tattoo ink into the spine and central nervous systems, and the potential contradictions that might cause.
That said, tattoo ink isn't just "floating around" under the skin. Macrophages assimilate the ink and it's pretty much stationary under the skin — tattoos are there for life you know! Outside of the fact that tattoo ink is on the whole inert, and there's only a tiny bit of it, it's not going to pour into your spinal column.
This is a non-risk entry. Unfortunately this urban legend is pervasive, as this reader describes,
"I am a 28 year old woman with tattoos on my upper and lower back. My husband and I plan to start a family in the next year or so and my 16 year old sister was just informed (through her high school life skills class) that women can not get epidurals if they have tattoos. It's pretty bad when this information is being told to young girls and if it's not even true. I didn't believe it when she told me, but she insisted that is was the truth because 'that's what she was told'."
Even some doctors not experienced with tattoos worry about this, as Sara describes,
"About a year ago I got a tattoo on my lower back, and late last year I had to undergo a spinal tap. The doctor made a huge deal out of it. He said the same thing that was said here, about the ink getting into my CSF — and it took him two mistakes before deciding to go through the tat, which to me was no big deal — it's a celtic knot... but he was pretty upset about it — needless to say I really didn't care."
Thankfully doctors are becoming better informed on the subject as Rosemarie (of Miraculous Creations) recounts,
"I am a heavily tattooed woman and own a studio in Worcester, MA. I recently broke my ankle severely and required surgery for plates and screws to be put in to rebuild the broken bones. I was given an epidural for my surgery and yes, my back is tattooed. Nothing was even mentioned to me about there being any issue. The surgery and epidural went very well. I kept sitting up and trying to watch the surgery over the little curtain divider they put over you, but they wouldn't let me watch. I suffered no ill effects from the epidural and my ankle is recovering slowly but surely."