Generally speaking, if a woman has unprotected sex, she can usually detect pregnancy with a test strip about 15 days after intercourse.
Pregnancy tests detect chorionic gonadotropin in the urine. The fertilized egg deposits in the uterine lining on about day 6, forming trophoblast cells that begin to secrete chorionic gonadotropin.
Chorionic gonadotropin levels in the urine are high at 15 days after intercourse, and measurement with test strips at this time can usually determine whether pregnancy has occurred.
If the test is done too early, it is easy to get a false negative due to low levels of the hormone in the urine. Early pregnancy test strips are easy and quick to detect pregnancy, but it is important to read the instructions carefully before using them, take the middle part of the first urine in the morning, and don’t soak the test strips in urine for too long.
If you want to know whether you are pregnant or not, it is recommended that you go to the hospital in time for blood HCG and ultrasound tests.