Because of your pregnancy, your body is more susceptible to infection. And the first thing that infection would affect is your blood and your blood obviously reaches your baby. It's a bigger risk, clean material or not. Legit artists will refuse to do tattoos on pregnant women, trust me, I've got 60% of my body covered. I've been to expos, plenty different shops, everything. They ask you to sign consent saying you are NOT pregnant. If you are, they won't take the risk.