HCG is usually not measured on the 3rd or 4th day of pregnancy, meaning that it is not possible to detect pregnancy.
After the formation of the fertilized egg, it gradually passes from the fallopian tube into the uterine cavity under the influence of peristalsis. Implantation gradually begins 6-7 days after fertilization, and after implantation, HCG can be detected as being in a pregnant state by a blood test after 7-8 days of gestation. It is therefore difficult to detect whether a woman is in a pregnant state on day 4 of pregnancy either by urine or blood test.
Since the fertilized egg does not enter the uterine cavity at this stage and there is no increase in human chorionic gonadotropin in the body, it is not possible to check for pregnancy. It is usually necessary to wait at least a week after intercourse and then a blood test for human chorionic gonadotropin can be taken to determine if you are pregnant, or you can test for pregnancy using a pregnancy test about two weeks after being in the same room.
If you suspect that you are pregnant, it is recommended that you seek medical attention in a timely manner so that a medical professional can determine whether you are pregnant or not, in order to avoid serious consequences such as miscarriage.