This is a glycoprotein composed of two subunits and secreted by the placenta. It is detectable 1 day after implantation of the a fertilized ovum and peaks at 60 to 90 days of gestation. Normal level is less than 5 mIU/mL; 20-100 IU/L 1 to 2 weeks after conception and 50,000 IU/L about 65 days after pregnancy then declines. In molar pregnancy, it can be extremely high initially, (over 100,000 IU/L) but declines with time. Normal Ranges: (in IU/L) non-pregnant: 0 - 5 possibly pregnant: 5 - 25 During Gestation: 0 - 1 wk: 5 - 50 1 - 2 wks: 50 - 500 2 - 3 wks: 100 - 1,000 3 - 4 wks: 500 - 6,000 1 - 3 months: 5,000 - 200,000 2nd trimester: 3,000 - 50,000 3 rd trimester: 1,000 - 50,000 In the first three weeks of a normal pregnancy, the serum beta hCG approximately doubles every two days. The doubling time of hCG is considered a more reliable method of evaluating an early pregnancy than a single result.