You hear about how pregnancy tests check for a pregancy hormone in your urine. But have you ever wondered what exactly this hormone is, and why it is only released during pregnancy?

Regardless of what brand of home pregnancy test you take, the test checks for the presence of the hCG hormone in the women's urine. So what is hCG? It stands for human chorionic gonadotropin, which is a glycoprotein hormone which is secreted by the placenta shortly after fertilization. Now you know why everyone just calls it the hCG hormone.

This hormone is only present after conception, which makes it an ideal way to check for pregnancy. It takes about 1-2 weeks for there to be enough of the hormone present in the urine to produce a positive test, which is why pregnany tests suggest waiting until at least the day your period is due.