The days when you had to go to a doctor for an expensive test to diagnose pregnancy are long gone.
Today you can go into any drug store, mega mart, or even some convenience stores, and buy a pregnancy test that is as reliable as the ones they use in medical offices.
You can even do an internet search to find out which tests are most accurate, and which can detect pregnancy the earliest. But have you ever wondered exactly how pregnancy tests, especially the newer digital pregnancy tests work?
When a woman is pregnant, she produces a special chemical known as human chorionic gonadotropin, or HCG.
A urine pregnancy test consists of a strip of absorbent material surrounded by a plastic case. This absorbent strip is impregnated with chemicals which react to other chemicals.
There are usually two different chemicals in the strip. The first one reacts to the presence of urine. This is usually the control line which lets you know that the test was working properly. The second chemical in the strip reacts to HCG.
When HCG is present in the urine, it reacts with the chemical in the absorbent strip to produce a positive result. A digital pregnancy test actually contains a small battery which powers the digital display.
It is only the display that is different with a digital pregnancy test; the underlying chemical reactions are the same. Knowing this, it may not make sense to spend extra money for a digital readout.
The amounts of HCG that a pregnancy test can detect vary from test to test. HCG levels increase in your blood and urine on a daily basis once your pregnancy has begun.
Usually it takes at least 10 to 14 days for enough HCG to be present in your urine to be detected by a urine pregnancy test.
Blood tests are more sensitive, but they are also more expensive and can be uncomfortable. Blood tests for pregnancy are usually ordered to monitor HCG levels rather than merely to detect their presence.
It is possible to get a “false negative” on a urine pregnancy test. A false negative means that you get a negative response but you are actually pregnant. This usually occurs early in your pregnancy which HCG levels have not risen to a detectable amount.
It is also possible, though less common, to get a “false positive” on a urine pregnancy test. A false positive means that you get a positive response when you are not, in fact, pregnant.
This usually occurs in response to medications you may be taking, such as fertility treatments. Generally, however, if a pregnancy test says you are pregnant, you can rely on the results.