What is the hCG hormone, and what role does it play in testing for pregnancy?

hCG is a hormone made by the placenta when you’re pregnant. It starts to be made just after the embryo attaches to the uterine wall, according to the Food and Drug Administration (FDA). 

When you’re pregnant, the hCG hormone increases very quickly. It typically doubles every 72 hours until it reaches its peak between eight and 11 weeks of pregnancy, according to the American Pregnancy Association (APA). 

hCG levels are what register positive or negative on a pregnancy test – both with an at-home urine test and a blood test. 

For more information about hCG and how it affects pregnancy tests, talk with your doctor. 

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