|MadSci Network: Medicine|
Hi Kelly, this is very good question and we are trying to answer it in our research at the moment. When you have sex you donít always get pregnant, if you do get pregnant then the new tiny baby will start to make a chemical (hormone) that keeps the baby alive. This hormone flows in the motherís body and when there is enough hormone we can see it in a special test. The test is performed on the womanís serum (from her blood) or on her urine if the test is positive we then know that the mother is pregnant. The problem is that each baby produces different amounts of the hormone so in some women we can see a positive test in less time that in others. To give you an answer, you can test positive for pregnancy in blood as early as 2 weeks after having sex (in some women). The hormone is made after about 5 days. Generally if you are pregnant most women will give a positive test after four weeks. The test is better in blood because there is more hormone at an earlier day, but after 5 weeks both blood and urine tests are good. Steve
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