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hCG: Human Chorionic Gonadotropin. It is a hormone produced by the placenta during pregnancy. Home pregnancy tests (HPTs) are designed to detect it.

Evaporation Lines

What are evaporation lines? On many tests if you don't read your test results within the test reaction time (usually 5 minutes) an evaporation line can develop as the urine dries on the test area. Evaporation lines appear to show up (or not show up) as a result of the composition of the particular urine specimen and they may appear on any test regardless of brand. It is always best to read your test within the specified time and then throw it away if it is not clearly positive. Yes, and leave it IN the garbage! No trash fishing later!

Evaporation lines are reported with most brands, and should be considered normal for home pregnancy tests. This is why tests should be read within the time specified within the instructions. Most recently we have had reports about the Inverness Medical tests different brands, AimStick, and dBest. Clearblue/ClearPlan sometimes has a white line where the result should appear, or a gray line without colored dye -- neither of which should be considered a positive result and require retesting.

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Faint Lines Within The Time Limit

If you get a faint line within the time limit, you are most likely pregnant. Home pregnancy tests contain a dye that is only activated by the presense of HCG in thr urine. This dye turns the result line pink or blue, depending on brand.

Test every other day as hCG double to see if the line is getting darker.

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What is a Chemical Pregnancy?

Unfortunately faint lines also appear with chemical pregnancies. A chemical pregnancy is when conception occurs, but the fertilized ovum fails to implant properly and the pregnancy fails to progress and menses occurs at the expected time or shortly thereafter.

Chemical pregnancy occur up to 50% of the time in a healthy fertile woman. It typically goes undetected when you are not watching your cycle so closely for pregnancy. Just because you get a faint positive doesn't mean that you are not pregnant. Sometimes we test too early and there is not enough hCG built up in your system to get a dark positive.

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All home pregnancy tests are NOT created equal

Pregnancy tests detect units of HCG (human chorionic gonadotropin) hormone in your system. The tests that detect the lowest number of units should be more sensitive and give you the earliest results. After Implantation occurs, HCG is produced, and that generally happens between 6-12 days . It takes a day or two for HCG to show up in your system, so if you implant at 6dpo, then you may show a positive at 8dpo.

Most women implant around 8 or 9dpo making twelve days past ovulation the most common time to get a positive. If you don't want to see a negative, you should wait until the first day after a missed period to test giving your body time to produce enough HCG to detect. Many women still show a negative result when they are indeed pregnant. If you test too early then you get to experience the heart break of see the - instead of the +.

Note: When testing early, it is important to use the first morning urine or no fluids or urination for four hours because you will get the most concentrate of HCG, you may get a false negative on any test if your urine is diluted.

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HCG Levels in Early Pregnancy

DPO=Days past Ovulation

*HCG is detectable in the blood serum of approximately 5% of pregnant women by 8 days after conception, and in virtually all the rest by 11 days. HCG rises progressively from conception. Levels double on the average, every 30.9 hours until values reach 6500 mIU/ml. Afterwards, HCG will double every 96 hours. After that the rate of rise becomes individualized, peaking between the 60th and 70th day (9 to 10 weeks) LMP. HCG decreases slightly between the 12th and 16th week post LMP, and then remains constant until birth.

*Levels for normal pregnancy fall within the following wide ranges. You will note a discrepancy between the ranges of normal in the table. The actual levels can vary widely, and is not as significant as the amount and rate of rise, particularly before 10 weeks.

*A blood serum level of less than 5 mIU/ml (5 IU/L) can be considered negative and anything above 25 mIU/ml (25 IU/L) positive for pregnancy. If you are unsure, repeat the test in two days to see if there is an upward trend, which indicates pregnancy.

* At 14 DPO, the average HCG level is 48 mIU/ml, with a typical range of 17-119 mIU/ml.
* At 15 DPO, the average HCG level is 59 mIU/ml, with a typical range of 17-147 mIU/ml.
* At 16 DPO, the average HCG level is 95 mIU/ml, with a typical range of 33-223 mIU/ml.
* At 17 DPO, the average HCG level is 132 mIU/ml, with a typical range of 17-429 mIU/ml.
* At 18 DPO, the average HCG level is 292 mIU/ml, with a typical range of 70-758 mIU/ml.
* At 19 DPO, the average HCG level is 303 mIU/ml, with a typical range of 111-514 mIU/ml.
* At 20 DPO, the average HCG level is 522 mIU/ml, with a typical range of 135-1690 mIU/ml.
* At 21 DPO, the average HCG level is 1061 mIU/ml, with a typical range of 324-4130 mIU/ml.
* At 22 DPO, the average HCG level is 1287 mIU/ml, with a typical range of 185-3279 mIU/ml.
* At 23 DPO, the average HCG level is 2034 mIU/ml, with a typical range of 506-4660 mIU/ml.
* At 24 DPO, the average HCG level is 2637 mIU/ml, with a typical range of 540-10,000 mIU/ml.

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Urine Test vs Blood Test

A blood test is more accurate, but not necessarily more sensitive. A lot depends on the lab. A quantitative blood test, usually called a beta hCG test, measures the exact units of hCG in the blood. That means it will detect even the most minimal level. There is another type of blood test sometimes called a qualitative hCG. This is a test that simply gives a yes or no answer to whether you are pregnant. Just like urine tests, labs vary as to what is considered a positive pregnancy test. Common cutoffs for positive are 5, 10, and 25 units. A level under 5 is considered negative. A test that is only triggered at 25 units of hCG is not any more sensitive than several of the urine HPTs. Blood tests should be repeated after 48 hours to confirm your beta numbers are rising, showing a pattern of a viable pregnancy.

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Retesting with an HPT and looking for a darker lines

You may get a darker line as your pregnancy progresses and your hCG increases, but the HPT is not accurate enough to give you a full picture, even though darkening tests are a good sign. Only a quantitative beta hCG blood test can tell you this. Best to have the blood tests performed at the same lab since standards vary.

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Pregnant without a positive HPT?

Most women will register on HPTs by the time they are a few days late for a period, but not everyone will. If you suspect you are pregnant, you should see your doctor for a quantitative hCG test no matter what result you get from an HPT.

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How soon can you test?

The earliest you can get a positive result on the most sensitive pregnancy tests is seven days after ovulation. Implantation needs to occur before hCG is produced, and that generally happens between 6-12 days post ovulation, usually by 10 days after.

For this reason, it makes economical sense to wait until 10-12 days after ovulation, but even then a significant percentage of women who are indeed pregnant will still show a negative result. If you have not had an hCG injection (common in fertility treatment, brands include Profasi, Pregnyl and Novarel), you can believe the positive, but you might get a false negative, however, this is rare. Again, if a line in the result window has a color to it, the dye has been activated and most likely means you are pregnant.

If your period is late, test again. Your hCG levels should double every 2-3 days and many people won't have a positive HPT until the first day of a missed period or even a few days later.

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False Results

From time to time women will indeed run into a bad test, however the chances of a false positive are very small. When in doubt, retest.