I use tea tree and lavender essential oils to keep my acne under control. I add a few drops of each to my moisturizer and/or add a few drops to a bottle of witch hazel and use that as a toner before moisturizing. Both of those essential oils are anti-microbial and safe during pregnancy.
Wife to my True Love since 8/03, Mom to DS 9/06, DS 5/08, DD 6/10, DS 11/11, and one on the way!
I use benzoyl peroxide on a regular basis to prevent mild acne, and when I became pregnant I researched it because it is really the only thing that works for me. There isn't a whole lot of data for its use during pregnancy, but what I have read suggests that the small concentration (2.5%) used topically is absorbed in such small amounts, and then broken down by the body, that it is highly unlikely to have a negative effect on the fetus. I know it's not entirely free from risk, due to lack of research proving it to be such, but I choose to take what I consider to be a small risk. With my DD i stopped using it for the first few months and had such bad acne that I was borderline depressed.
Mama to Conejita 2/2/10 and Little Stinker 6/28/13. Expecting a surprise in late March!
I would have her try the Yes to tomato products. Read the ingredients first but I'm pretty sure they're without chemicals. I could be wrong. http://www.yestocarrots.com/category/acne-prone-skin?category_id=0000041&nav_id=0000017