The hCG hormone level in the human body doubles approximately every 2.2 days during the first trimester of pregnancy. Detectable levels of hCG start at 5 mIU/ml during the first week of gestation and rise to 100,000 mIU/ml at 2 to 3 months. Values decline to 10% to l5% of peak concentrations during 2nd and 3rd trimesters. In normal circumstances, first morning urine samples approximate serum hCG levels which reach 5 to 50 mIU/ml within one(1) week of gestational age.
The above table shows the typical ranges in hCG levels during pregnancy. *Statistically, the ranges are necessarily broad as each pregnancy cycle and hormone level is unique to the individual and extreme readings either way are possible in a very small percentage of pregnancies. However the table does clearly indicate the rapid increase in hCG hormone during the first trimester.