I have had acne and decided to get an OTC medication called Proactive (advertised on Television by Vanessa Williams). It does not say that it poses any danger to my baby as I am six months pregnant, but I want to make sure that it is safe to use such a product.
You've got to check the ingredients. The company producing the product should be willing to list them. Certainly you want to stay away from anything with Retin-A or other Vitamin A derivatives, and any antibiotic components need to be cleared with your doctor. Astringents (skin tighteners) aren't harmful.
There is a new light therapy some dermatologists use that is safe in pregnancy. The results are mixed, but a lot of women get better results with this than the creams and other medicines. You might want to ask around.