Unit conversion: 1IU=1000mIU
3--4 weeks: 9--130;
4--5 weeks: 75--2600;
Gestational 5--6 weeks: 850-208003;
6--7 weeks: 4000--100200;
7--12 weeks: 11,500 -- 289,000;
12--16 weeks: 18300--137000;
16- 29 weeks: 1400- 53000;
Gestational 29--41 weeks: 940-- 60,000.
HCG increases rapidly in the serum during the first trimester, doubling in about 1.7 to 2 days, reaching its peak at 8 to 10 weeks of gestation, and then decreasing rapidly after 12 weeks, and then maintaining a certain level.