Obstetricians have many tools available to help them determine pregnancy and monitoring gestation. The simplest home pregnancy test can detect the pregnancy hormone, hCG, but it cannot provide any more information beyond "positive" or "negative." In reality, hCG can offer a glimpse into the early stage of pregnancy and give valuable information to the doctor and to the parents.
Identification
Human chorionic gonadotropin, or hCG, is the pregnancy hormone produced by the placenta and is the chemical that urine and blood tests use to confirm a pregnancy. Levels of hCG can be detected by a blood test about 11 days after conception, and a urine test can detect it at about 12 to 14 days. An hCG level of less than 5 mIU/ml is considered negative and a result greater than 25 mIU/ml is positive.
Types
There are two types of hCG tests. A qualitative hCG measures whether hCG is present in the bloodstream and offers no further diagnostic information. A quantitative hCG measures how much hCG is in the blood and provides a doctor with basic pregnancy information. A qualitative hCG will tell you that you may be pregnant, but a quantitative hCG could indicate if the pregnancy is progressing normally, whether there are multiple embryos, or if further testing is needed. When gathering quantitative hCG levels, tests must be done over the course of several days to obtain the necessary information.
Significance
The level of hCG in a woman's blood is an early indicator of pregnancy and how well it may be progressing. It also may indicate multiple pregnancies or a potential problem, all based upon the levels of hCG in the blood. In a normal pregnancy, hCG levels will double every 48 to 72 hours. There are ranges for normal levels in each week of pregnancy, although it is more important that the numbers are increasing normally rather than if they fall within a specific range.
Considerations
Low hCG levels could be an indicator of several issues. Early pregnancy tests will reveal low hCG levels. It is common to miscalculate when conception occurred resulting in lower numbers than anticipated. If hCG levels are not doubling within a 48 to 72 hour period that may indicate a miscarriage, blighted ovum or an ectopic pregnancy. Pregnant women who are smokers will often have lower than normal hCG levels, as much as 21.5 percent lower, than the average pregnancy at the same gestation.
Time Frame
Many women experience anxiety early in pregnancy, due to concern about hCG level results. The discriminatory hCG Zone is when hCG levels indicate the embryo has grown enough to allow doctors to see a gestational sac on ultrasound. This hCG level is between 6,000 mIU/ml and 6,500 mIU/ml and, while it does not guarantee a successful pregnancy, it is a benchmark in monitoring gestation. When that period of development is reached where the hCG levels are increasing as expected and a sac is visible on ultrasound, along with a heartbeat, parents often feel great relief.
