How Pregnancy Tests Work

To check and see whether you are pregnant or not, you can use 2 main pregnancy tests that are available — urine tests and blood tests. Usually, both of them report results with high accuracy. However, it might not always be clear how the results are made. 5-Minute Crafts wants to reveal all the pregnancy tests’ secrets and explain to you how they work.

The important hormone

Both at-home and blood tests work similarly. They are needed to detect a special hormone for the maternal recognition of pregnancy — human chorionic gonadotropin (hCG). When the embryo attaches to the uterus, the production of hCG is triggered. Its concentration in the woman’s body gradually grows until weeks 10-12 of pregnancy and eventually reduces at the end. There are some pregnancy tests that can determine hCG levels around 8 days after fertilization.

At-home pregnancy tests

Pregnancy tests that you can use at home are easy and convenient. They allow you to check the hCG levels in your urine. Usually, you can buy them in pharmacies and drug stores and use them at your discretion.

Step 1: You need to apply your urine to a sample pad (usually it’s on the end of a test stick).

Step 2: The liquid moves to the reaction zone.

Step 3: If the hCG is present in your urine it will bind with special antibodies with different enzymes that react to it. The existence of hCG will also trigger a color change in dye molecules inside the test strip, which will result in the first stripe appearing if a woman is pregnant.

Step 4: The liquid will keep moving forward on the test strip and reach the control zone where it triggers a color change. So, another line will appear no matter whether the woman is pregnant or not.

🧪 1 line on the test strip — the woman is not pregnant.

🧪 2 lines on the test strip — the woman is pregnant.

When you perform this test at home, keep these tips in mind:

1. It is best to use your morning urine because the concentration of hCG is the highest in it. If you do it during any time of the day, make sure that you haven’t emptied your bladder for at least 4 hours.

2. Before you take the test, do not drink excessive amounts of liquids as they can dilute hCG levels in your urine.

Blood pregnancy tests

Your doctor can help you by taking a sample of your blood with this type of pregnancy test. It works similarly to at-home done tests as they check for hCG levels in your blood. This kind of testing is performed by medicals specialists in a lab. A blood test is a bit more sensitive to hCG and thus more precise than checking your urine. Also, it can provide you with reliable results earlier — within 9-12 days after conception.