Blood HCG is also known as human chorionic gonadotropin. The normal value of blood HCG is 0-5 U/L. If it is lower than 5 U/L, no pregnancy has occurred, but if it is higher than 5 U/L, conception has occurred. When an ectopic pregnancy occurs, the first thing that happens is that the blood HCG is not significantly doubled, or even higher or lower than the normal value of blood HCG. When the blood HCG is drawn and tested, it can be used to determine some preterm abortions. When a preterm abortion occurs, the dose of birth control medication can be given through the blood HCG value. Also, the blood HCG should be taken about 8 days after intercourse to avoid prematurely affecting the test results.