Most Crohn's disease patients will take several different medications at the same time. Sulfasalazine and its cousins are for flare-ups in the colon. Metronidazole is an anti-biotic that helps keep infections of the diseased tissues under control. Steroids typically added when all of the above are not enough. Immunosuppressive therapy is sometimes added to the mix.
Surgery is likely for the majority of patients at one point or another.
The surgery will remove the severely affected and damaged sections of bowel. It is done as a last resort. For pregnant women, sulfasalazine and steroids are safe to use. Folic acid supplements, ideally before becoming pregnant, are in order. But, metronidazole and immunosuppressives can harm fetus or nursing baby.