Pregnancy testing is not routinely performed in women below 50 who are attending for colonoscopy but should be performed when fluroscopy may be performed - please see attached 2014 guidance for the ASGE.
However, there should be availability of test kits should there be a query regarding pregnancy to give the patient choice of going ahead or declining the procedure. It is safe to do colonoscopy in pregnancy but there would be risks associated with the drugs. Now we have access to Entonox this could be an option (but not in the first trimester).