Suspected pregnancy is identified with a combination of lab work and ultrasound examination. 

Detection of human chorionic gonadotropin (hCG) in blood or urine  is used to screen for pregnancy. Blood levels of hCG double every 1-2 days in the first month of pregnancy, peaking in concentration at 8 to 10 weeks of gestation.

Detection of hCG  in the urine with a home pregnancy kit is less accurate and maybe negative compared with measurement of hCG in the blood due to the inability of the urine test to detect very low levels of hCG.