There is no known facts on tanning while pregnant! The only thing that could be wrong is getting hot, but your going to get hot outside faster than some of the more modern beds. The UV light only penetrates the first 2 layers of the skin. The tanning bed is not like a microwave, the uv rays are not going to cook your insides. I am a manager at a tanning salon and have been doing it for quite some time and at our salon we have a 10min bed that you dont get hot in at all, so I have been tanning in that, I think that it is a lot safer to tan in a controlled environment than outside where your getting exposed to many different types of rays and have more of a chance of over exposure. I did cut back on the amount I used to tan prepregnancy, but until they have proof that there is something wrong with it than I will continue. Everyone knows that the world is completely anti tan because of the obvious, but if you are in a tanning bed it is much more controlled therefore safer. Another problem I could think of is actually getting out of the bed, I struggled with that a little today
Also if your worried about why the owners of tanning salons dont let pregnant people tan it is because they do not want to be liable if something does happen to your unborn child. because there is not very much research on the situation they dont want to be accused and possibly sued for whatever is wrong with the baby because at this point the moms to be can say anything that happened to them while they are pregnant and tanning is because they tanned.