A blood test for pregnancy is also known as a blood test for HCG. The normal value of blood HCG is 0-5 U/L, if the value is greater than 5 U/L it confirms pregnancy, if the value is within the normal range it can be excluded. After pregnancy, you can monitor the blood HCG level, that is, repeat the test after an interval of 2-3 days, and the HCG value can reflect the activity of the embryo. Generally, HCG doubles with time after pregnancy, and a doubling of HCG confirms that the embryo is very active. However, ultrasound is necessary to confirm an intrauterine pregnancy and to exclude ectopic pregnancy, gestational trophoblastic disease, and vacuolar pregnancy.