Pregnancy & Baby 

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How do pregnancy tests work?

There are several varieties of pregnancy tests. Some are used in home testing and some are done in a laboratory. Some tests are done on urine and some on blood. All of the commercially available tests detect HCG (Human Chorionic Gonadotropin), a hormone produced during pregnancy. This substance is produced upon implantation of a fertilised ovum. A sensitive blood or urine test detects this substance as early as eight to nine days after ovulation.

In the home tests, you use a wick, which is in contact with a membrane. If the urine contains HCG, it will react with an antibody on the latex, and a coloured line will form. Home tests, if done exactly according to instructions, claim 97 percent accuracy, That’s not bad. But in one study I read, there was a large percentage of false negatives and a significant (though smaller) number of false positives. This was mostly due to poor technique or doing the test too soon following conception.

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