Sounds like your uc is simmering, not in remission. Untreated, simmering uc inflammation can greatly increase the odds of landing in a flare, uc often spreads in extent and severity when not fully treated ...
Here's some info on uc medications and pregnancy:
From conception to delivery: Managing the pregnant inflammatory bowel disease patient
www.wjgnet.com/1007-9327/pdf/v20/i13/3495.pdfThe Second European Evidenced-Based Consensus on Reproduction and Pregnancy in Inflammatory Bowel Disease
ecco-jcc.oxfordjournals.org/content/eccojc/9/2/107.full.pdf