There are several types of pregnancy tests available to women who suspect that they are pregnant. All pregnancy tests are based on the presence (or lack of) hCG. hCG is a hormone that is released by the placenta, and is present in a pregnant woman's blood and urine. hCG can be found in a woman's blood through a simple test performed by a doctor. A doctor can take a blood sample, send it to a laboratory for analysis and have an answer within one to two days.
Doctors can perform two types of pregnancy tests: the first simply tests for the presence of hCG (to inform a woman whether she is pregnant or not), while the second measures the amount of hCG (to inform a woman how far along she is in a pregnancy).
Normally, a woman will perform a home pregnancy test before having the result confirmed by a doctor. Home pregnancy consist of a strip with a tip that can detect hCG in the urine. A woman can either urinate directly on the tip, or into a cup and then dip the tip into the urine. Once the tip has been saturated, a result will be displayed within five minutes.
It's important to consult the instructions when interpretting a test. While a regular home pregnancy test can detect pregnancy on the first day of a missed period, an early pregnancy test can detect hCG four to eight days before a missed period.