The earliest you can determine if you are pregnant is about 8-10 days after intercourse by having a blood test for human chorionic gonadotropin. If you want to use a pregnancy test, you should wait 12 days after intercourse before you buy a pregnancy test to detect pregnancy. If the test results are outside the normal range, you are pregnant. If it is within the normal range, you are not pregnant and should wait patiently for your period. If it is the case that the pregnancy needs to continue, it is also counted orally first if possible, so as to prevent fetal neural tube malformation. Also, when you are about 45 days pregnant, you can go to the hospital to register for an ultrasound in the obstetrics department to determine whether the pregnancy is intrauterine or ectopic. Because not all pregnancies are intrauterine, this will ensure a stable and healthy fetus.