Pregnancy can be detected about 1 week after intercourse, but a blood HCG test is required. If you use a pregnancy test, it is basically undetectable because the HCG in the urine has not changed significantly at this time, so there is basically no reaction when you use a pregnancy test. If you want to take a test, you can wait for 7 days after your period is delayed and then go to the hospital to take a test, the results are relatively accurate. After intercourse, the fertilized egg will gradually settle, and after it settles, the hormones in the body will change due to stimulation of the body organs, and the HCG in the body will grow slowly after it settles, and the growth rate is faster until 6-8 weeks of pregnancy. However, after the 8th week, the rate of increase will gradually slow down and then return to normal.