The precautions for stool screening mainly include paying attention to the diet before the test and the time of delivery. 1. Pay attention to the diet before the test: it is better not to eat animal offal or animal blood before the test, because the above foods may cause false positive fecal occult blood test. 2. Pay attention to the time of delivery: generally the time of retaining the stool can be random, but generally the time of delivery is required not more than 2 hours, if more than 2 hours may cause changes in the formation of fecal components, resulting in errors in the examination. The time requirement is even more stringent for tests such as trophoblast observation. If stool screening is needed, it is important to follow your doctor’s instructions on how to prepare for the test so that the test is not performed properly and your condition is not delayed.