It is not possible to detect pregnancy by blood test at 1 week of pregnancy because the production of human chorionic gonadotropin has not yet reached its peak at 1 week of pregnancy and the amount is small, so the result of the measurement may not be accurate, and it is recommended to repeat the test after 2 to 3 days. A blood test to determine if you are pregnant is done by measuring the value of human chorionic gonadotropin in your blood. In normal early pregnancy, human chorionic gonadotropin (HCG) starts to be secreted around the 6th day after fertilization of the egg, and can be detected in the blood from the 7th day onwards, with a rapid rise in serum HCG levels by the 8th to 10th day. The most correct and reliable way to diagnose early pregnancy is to perform ultrasound, the earliest time is about 1 week after the menstrual period is delayed, the ultrasound screen can show a circular halo in the uterus, also known as the gestational ring, the dark area inside the ring is amniotic fluid, 8 weeks of pregnancy ultrasound can be seen in the rhythm of the fetal heart beat. Vaginal ultrasound can diagnose early pregnancy one week earlier than abdominal ultrasound, and the presence of a gestational sac in the uterus is the earliest image to appear in ultrasound diagnosis.