HCG refers to presence of the hormone human chorionic gonadotropin, which undergoes dramatic increase when women are pregnant. Tests to determine pregnancy often look for HCG levels to hit a certain spot, and even without pregnancy, some women have a tiny amount of this hormone. It can measure at about 200 nanograms per milliliter (ng/ml). Women who take pregnancy hormones may have much higher start points in HCG levels and it may be difficult to determine pregnancy, especially in early stages. In these cases, false positive tests can be fairly common.
As pregnancy progresses, HCG levels rise dramatically. Early on in the pregnancy, they can easily double every few days. Declining levels or levels that don’t increase after pregnancy is confirmed might suggest problems with the pregnancy and are sometimes indicators of miscarriage, but could also be an error in calculating the date of conception. Women should understand though, that measurement of HCG is not precise and different labs may sometimes get different results. Some women’s HCG doesn't climb as fast and yet results in healthy pregnancies, and drops in levels might mean no more than a laboratory error.
When evaluating charts to determine health of pregnancy, women need to know that especially as pregnancy progresses better methods exist for determining health of a child. Also bear in mind that a single HCG levels test says very little about a pregnancy. Lastly, since levels can vary so greatly at early stages in the pregnancy. they may not adequately date it.
On charts that may assign normal HCG levels by pregnancy week, measurements are in mili-international units per milliliter, or mIu/ml. Non-pregnant is often defined as anything below 5 mIu/ml. By three weeks after date of last period, the levels might still read at 5 or have climbed up to 50. At 4 weeks, they could again still be 5 or up to the mid 400s.
As weeks progress, the following progression of levels might occur:
- Week 5: 18-7,340 mIu/ml
- Week 6: 1080-56,600 mIu/ml
- Weeks 7-8: 7,650-229,000 mIu/ml
- Weeks 9 to 12: 25,700-288,000 mIu/ml
- Weeks 13-16: 13,300-254,000 mIu/ml
- Weeks 17-24: 4,060 - 165,400 mIu/ml
- Weeks 25-40: 3,640 - 117,000 mIu/ml
When people look at the progression of HCG levels, it reveals a lot. First, variance in levels is huge. At week six, women could have a blood serum measurement of 1000, or fifty times that. This should suggest that testing HCG is not a fully adequate means of assessing pregnancy. It cannot be stressed enough that the norm is truly variable and pregnant women concerned over this issue should seek advice from their doctors about what other accurate tests may be employed to determine things like due date and health of the pregnancy.