HCG LEVELS IN PREGNANCY

hCG (human chorionic gonadotropin) is a hormone produced by the placenta during pregnancy. Home pregnancy tests (HPTs) and Blood serum tests are designed to detect it. hCG is detectable in the blood of pregnant women by 8-10 days after ovulation and the majority by 12 days past ovulation. This is when the embryo burrows itself into the lining of the uterus. This is also know as implantation. HCG rises progressively from conception. Levels double on the average, every 31-48 hours as the embryo grows until values reach 6500 mIU/ml (6,500 IU/L) at approximately the eighth week after the last menstrual period (LMP). After that the rate of rise becomes individualized, peaking between the 60th and 70th day (9 to 10 weeks) LMP (Last Menstrual Period). HCG decreases slightly between the 12th and 16th week post LMP, and then remains constant until birth.

Source: http://www.advancedfertility.com/earlypre.htm