Pregnancy test paper detection may be caused by the following reasons: 1, may be caused by the detection time is too early, generally HCG will appear in the urine a few days after the fertilized egg is laid, if the pregnant woman is detected too early, it will not be possible to detect pregnancy, women with long menstrual cycle or abnormal ovulation will be detected only about 40 days after menopause; 2, drinking too much water may lead to dilution of urine, which will If pregnant women test at night, it may affect the accuracy of the results. It is recommended that pregnant women test in the morning, when the HCG content in the urine is higher; 4, pay attention to the quality of the test strips, if the test strips are out of date or damp, it may lead to undetectable pregnancy, so pay attention to the production date when buying test strips, so as not to affect the results of the test.