I did a study on the electromagnetic spectrum focusing on UV rays in university for one of my labs, and in my discussion section I related the material to tanning beds.
Trust me, after that I would never tan in a salon (or outside for that matter) again!
UV rays in normal tanning conditions (outside) cause many effects. Some good. Most bad. For example.....Exposure to UV rays for ten minutes causes the vitamin D production needed for an entire day - that's good. UV radiation causes DNA mutations and also causes local or systematic immunosuppresion - that's bad!
The average tanning bed has 15x the level of UV radiation than what you would get if you were outside.
Pregnant women are already immunosuppressed to begin with and getting sick right now is easier than ever already. That in itself is a pretty solid reason to stay away. Not to mention the sensitive skin, or the folic acid deficiency caused by UV that could cause birth defects, like the_girlfriend said.
All in all, it's better to go with tan in bottle, lol!
Check out this video, it's kinda cool.
http://www.cnn.com/video/#/video/health/20
07/12/19/gupta.indoor.tanning.cnn?iref=vid
eosearch