Generally, pregnancy can be detected as early as one week and as late as three weeks after intercourse. First of all, you can take a blood test for HCG one week after intercourse to detect whether you are pregnant or not. Secondly, you can take a urine test through early pregnancy test paper or pregnancy test stick, and generally choose morning urine for the best effect which is more accurate. In addition, after intercourse, a week after the delay of menstruation, you can test whether you are pregnant, so women who are preparing for pregnancy should not be too anxious, the longer you wait the more accurate the pregnancy test.