Human chorionic gonadotropin (HCG) is a hormone produced during pregnancy. HCG is the hormone measured in pregnancy tests. A level less than 5mIU/ml is considered negative for pregnancy and anything over 25mIU/ml is considered positive. Urine tests for HCG (home pregnancy tests) are able to detect different levels of HCG. The most sensitive tests can detect levels as low as 25mIU/ml and can be effective as early as 11 days after conception. Blood tests are more sensitive than urine tests and can detect pregnancy sooner.

Your doctor can order two different types of HCG tests. A qualitative HCG test is usually used to determine if you are pregnant. A quantitative HCG test is used to determine how much HCG is present which can help determine the viability of the pregnancy. HCG is produced by the placenta as the baby develops. The amount of HCG doubles approximately every 48-72 hours during the first 8 to 11 weeks of pregnancy. As the end of the first trimester nears, the HCG levels begin to decline and level off.

An HCG quantitative test will tell you how much HCG is present in your blood. When the placents is not developing normally, the HCG levels do not rise as they should. This may mean that the embryo is not viable and that a miscarriage is likely. However, HCG levels vary widely and many normal pregnancies have low HCG levels. One HCG test does not tell you much. It is not an accurate way to date a pregnancy - an ultrasound at 5-6 weeks is much more accurate. Two HCG quantitative tests 48 hours or more apart can give you an idea of how healty the pregnancy. HCG levels usually double every 48-72 hours. So, seeing that your HCG levels are rising can indicate a healthy pregnancy.

What if your HCG levels are lower than expected? While this could mean a problem with the pregnancy, quite often it is simply that the dates are wrong. I spent a difficult weekend worrying about a miscarriage only to have an ultrasound show that the dates were off by 12 days, making my HCG levels high for the actual gestational age not low! It is important to talk to your doctor since a low HCG level can indicate a problem such as an ectopic pregnancy.

What if your HCG levels are higher than expected? Again, this could mean that the dates were miscalculated. It may also mean a multiple pregnancy or a molar pregnancy.