Pregnancy tests measure levels of human chorionic gonadotropin (hCG). Since hCG is produced by the placenta, it is only present in pregnant women. The anticipation of being pregnant makes it difficult for some women to wait until a missed period to take a pregnancy test. If you are one of these women, several pregnancy tests are marketed as being able to detect a pregnancy before a missed period. Although having this option may be a blessing, it may also add to your anxiety, depending on the results.
hCG levels
As soon as the fertilized egg attaches to the uterus, the production of hCG starts. This occurs about a week after ovulation. From here, about every two to three days hCG levels double. The higher your hCG levels, the more accurate an early pregnancy test will be for you.
Urine Tests
To get the most reliable test result, you want a test that measures hCG at the lowest levels possible. Most urine tests that advertise as being able to detect a pregnancy before a missed period are able to detect hCG at 100 mIU/ml or lower. The earlier you are testing, the lower you want this detection to be. Some tests advertise the ability to detect hCG levels as low as 20 mIU/ml. The advantage of using a urine test is that these are readily available and give almost instant results. However, you have to read and follow the directions carefully; incorrect use can give you inaccurate results.
Blood Tests
Your doctor can order a blood test as early as a week after conception. There is little room for error in a blood test. It can detect the hCG in your blood as early as seven days after conception, states the American Pregnancy Association. The disadvantages are the day or two wait to get the test back and the expense of the test.
Test Result Accuracy
Urine tests are less accurate than the blood tests for early pregnancy detection. Most urine early pregnancy detection kits show that only about 50 to 70 percent of the time is a pregnancy detected four to six days before a missed pregnancy. This means that 30 to 50 percent of women in the research got a false negative result when using an early urine test. The percent increases closer to the expected period date and with urine tests that detect a lower level of hCG.
Negative Result
The possibility of getting a negative test result is much higher when testing this early. A negative pregnancy test, before a missed period, does not necessarily mean you are not pregnant. It simply means that hCG has not been detected. If you are truly pregnant, your hCG levels just may be too low to detect this early. Wait several days to test again if you get a negative result.
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