There are many different tests that can be done during pregnancy, starting from home pregnancy tests to let you know if you are pregnant, or not to tests done in the 3rd trimester to check the health of the fetus.

Home pregnancy tests detect the presence of the pregnancy hormone called human chorionic gonadotropin (hCG) in your urine. 

Other pregnancy or prenatal tests are done for many diferent purposes, especially when there are concerns for mother's or fetus' health.