After the patient is pregnant, the use of test paper can not be measured mainly for two reasons: First, the measurement of the time is not appropriate, if the use of urine pregnancy test to detect is not pregnant, at least one week after ovulation, or not to determine the ovulation of the case of the last coitus 10 days after the last time, this period of time to check the accuracy of the urine pregnancy test will be relatively high. If the time to detect the urine pregnancy test is within a week after intercourse, this case will not be detected, because at this time, the fertilized egg has not yet implanted, blood or urine HCG levels have not yet risen, so the detection can not be detected. Secondly, it is considered that the test paper used by the patient may be of poor quality or there are problems with the testing procedure, resulting in inaccurate results and false negatives, which can be confirmed by checking the blood chorionic gonadotropin.