Most of the women who think they are pregnant, but are not sure, use home pregnancy tests. But how many of them know how these tests work and if the result is true or not? Well, first of all a woman should know when the test must be taken and which are the best home pregnancy tests.

So, the first think to know is that these tests detect the pregnancy by measuring the presence of a hormone in the urine. The hormone is called chorionic gonadotropin, and is a telltale hormone. But how can this hormone tell you if you are pregnant or not? Well, this hormone is produced by the placenta. When the egg is fertilized and finds it' s place in the uterus, this hormone is released into the bloodstream. This usually happens about six days after the egg has been fertilized. From that point the amount of this hormone in the body is doubled every two days. So in about fifteen days after the fertilization took place, the home pregnancy test should be able to indicate if your are pregnant or not. But it all depends on the test. It is said that most of them are not sensitive enough to detect a pregnancy even at that stage. For better and certain results it is indicated you should take the test a week after your the day that you were expecting your period.

It was believed that home pregnancy test were very accurate, almost 100 percent, even taken the day when a woman misses her period. Later studies have shown that this belief was misleading. The amount of the telltale hormone in the urine can differ from a woman to another very much. It can be different in any given days after the implantation had taken place. Studies have been made on different groups of women, and reaschers discovered that the home pregnancy tests are not sensitive enough to detect a pregnancy in the first day that the woman missed her period. It worked for almost 15 % of the tested woman. But the the same home pregnancy tests showed to be very precise when taken seven days after the menstrual period was expected.

Of course when reading this, one would wonder why these tests claim to be so accurate, if they are not? Well the fact is that the ninetynine percent accuracy that this tests pretend to be is because the sensibility of the tests can detect a pregnancy, but not in it's first days or in the first day of the missed period. The home pregnancy tests can determine a pregnancy, but it matters when this test is taken. To find out how to choose a pregnancy test and use it, be sure to read part two.