I have crohn's disease. i am pregnant. i take medicines containing active ingredients namely: mesalamine and prednisaolone. are they harmful to foetus?

Nope, they are safe.: You should continue both medications and seek gastroenterology and maternal-fetal medicine care asap. They are both safe for the fetus, although chronic steroid use increases your chances for osteoporosis, diabetes mellitus, hypertension and gastritis. If you we're in remission of your crohn's disease for 6 months before conception you should expect smooth sailing until delivery. Take folic acid!