In most cases, pregnancy cannot be detected on the 9th day of intercourse because the sperm and the egg have to enter the uterine cavity after the union and the trophoblast begins to secrete blood HCG only after the implantation. Clinically, due to individual differences, some people can detect pregnancy through blood HCG on the 9th day of intercourse, which accounts for a very small percentage of the cases, mainly because the fertilized egg enters the uterine cavity at different speeds under the peristalsis of the fallopian tube. If you are not in a hurry, it is recommended to have a blood test for HCG about 15 days after intercourse. If you are expecting a child, you can also have a blood test 9 days after intercourse to find out if you are pregnant.