If a pregnancy test cannot detect pregnancy even though the period has been delayed for several days, there are three possibilities to consider: first, the patient herself is not pregnant because the appearance of delayed period does not mean that the patient is pregnant, it can be normal menstrual fluctuations, such fluctuations are normal as long as the period is delayed within 7 days; it may also be considered that the patient’s period is irregular and appears to be delayed. Secondly, it is considered that the patient is pregnant for a relatively short period of time, so it is not detected by using test paper. It can happen during the safe period because ovulation occurs disorderly in women, and there is also impromptu ovulation in women. If this pregnancy is late and ovulation is still within a week after a few days of delayed menstruation, it is impossible to detect pregnancy using test strips in this case. Third, the patient is considered pregnant, but the quality of the test strips is not good or there are mistakes in the testing process, so there is a false negative result, you need to monitor the urine again on the next day, or go to the hospital to check the blood chorionic gonadotropin for confirmation.