The main reasons why the test paper does not deepen after in vitro fertilization are improper operation method, too early detection time and unsuccessful transplantation and other factors. 1. Improper operation method: early pregnancy test paper detects the change of HCG in urine, if it shows positive, it means that the chance of conception is greater, if the operation method is not appropriate, it will affect the test results. 2. Early detection time: It usually takes 1~5 days for the embryo to begin to implant after transplantation, and some will be a little later, there are individual differences. If the test time is too early, the test paper will not deepen. 3. Unsuccessful transplantation: If the test paper does not deepen, it may be due to unsuccessful transplantation, and the woman has not successfully conceived. If you find that the test paper is not deepening, it is recommended not to worry too much, pay attention to rest and avoid sex, which will help the success of embryo implantation.