Two good reasons not to get a tattoo.
Tattooing inks have changed a great deal over the years and many modern tattoo inks contain organic azo dyes with plastic-based pigments that are also used industrially in printing, textiles and car paint. Many unknowns exist about how these new tattoo inks interact with the skin and within the body.
Allergic reaction to the tattoo pigments is one of the most common problems associated with tattooing. Infections also can pose a serious threat to health. Along with localized bacterial infections, there have been reports of people being infected with syphilis and hepatitis B and C due to non-sterile tattooing practices, Shinohara said.
Skin cancer is another potential risk associated with tattoos because they can make it hard to detect cancer-related changes in moles. If you get a tattoo, make sure it's not placed over an existing mole.
A tattoo can also cause a reaction that creates a bump that resembles a type of skin cancer called squamous cell carcinoma. Because it is hard to distinguish from skin cancer, the bump could lead to potentially unnecessary and expensive skin cancer treatment, including surgery, Shinohara said.
http://www.everydayhealth.com/skin-...=maing-grid7|main5|dl24|sec3_lnk2&pLid=277466
If you have a lower back tattoo and decide to have an epidural during labor, the anesthesiologist will likely try to insert the needle through skin that isn't tattooed — such as an open area in the tattoo design.
If that isn't possible, the anesthesiologist might nick your skin before inserting the needle. This reduces any possible risk associated with trapping tattoo pigment inside the needle or depositing the pigment into deeper tissues.
http://www.mayoclinic.com/health/lower-back-tattoo/AN01357