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Analytical Chemistry

Analytical Chemistry in Our Lives

How does a pregnancy test work?

A pregnancy test works by detecting a hormone called human chorionic gonadotropin (hCG) that is produced in the placenta after fertilization. The hCG hormone will be present in the blood and urine about a week after conception, and it’s detected by an indicator molecule on the pregnancy test that changes color upon binding to hCG. The tests you can buy in the store are actually pretty similar to those used at a doctor’s office; both are based on hCG binding to a chemical indicator that changes color. The main difference is that the doctor’s office has technicians who are more familiar with using the tests, so there’s less chance of a mistake with using or interpreting the test.



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