Is it possible to detect pregnancy after four days of menstruation?

For women with regular menstrual cycles, pregnancy can be detected by delaying menstruation for four days. As early as seven days after fertilization, human chorionic gonadotropin (HCG) can be detected from pregnant women's blood and urine. HCG concentration in early pregnancy increases gradually with the extension of pregnancy time. It is relatively simple to check HCG in urine through early pregnancy test paper to help determine pregnancy. When urine shows HCG and reaches the detection threshold of early pregnancy test paper, early pregnancy test paper will show two bars, that is, positive results. Generally pregnant women can check positive results after 2-3 days of menstrual delay. In addition, HCG in blood can also be checked to determine pregnancy. Blood HCG is quantitative detection, that is, the result is a specific value. Blood HCG is more sensitive, can be found earlier pregnancy.