Home Pregnancy Tests allow you to determine if you are pregnant or not by detecting the hormone hCG in a woman's urine. Though easy to use, there are a number of common, frequently asked questions about pregnancy tests - and how they can be most effectively used.
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Q: How do home pregnancy tests detect pregnancy?
Home pregnancy tests detect the presence of the hormone hCG in a woman's urine. HCG (human chorionic gonadotropin) is a glycoprotein hormone secreted by the developing placenta shortly after fertilization.
Once the egg implants in the uterine lining, hCG is produced and secreted by the placenta. hCG can be detected in blood samples and in urine samples. Urine pregnancy tests detect hCG and will indicate a positive result when the hCG level in a sample reaches a specific threshold. If the amount of hCG in the urine sample is sufficient to exceed the threshold - or sensitivity level - a "test line" will appear indicating a positive result. If the hCG quantity in the urine sample is below this sensitivity level, no test line will appear, indicating a negative result for pregnancy.
Q: Does the hCG sensitivity of the test matter?
The sensitivity of a pregnancy test determines how soon after conception pregnancy can be detected by the diagnostic kit. Concentrations of hCG are reported in milliInternational Units (mIU) or amounts equal to 1/1000th of an IU per milliliter. Pregnancy tests with a sensitivity of 20 mIU/ml are more sensitive than tests with 50 to 100 mIU/ml.
With 20 - 25 mIU/ml tests, high sensitivity equates to early detection of pregnancy. That means you can begin testing accurately as early as eight days after conception. Conception may take place several days after date of intercourse, so the date of intercourse should not be viewed as the necessary day of conception.
Q: How accurate are home pregnancy tests?
Under laboratory conditions, home pregnancy tests are 99% percent accurate. Inaccuracies are most often traced or errors in application or failure to follow instructions with care. There are circumstances and variables - discussed in questions below - that may impact pregnancy test results (from fertility medications to dilution of urine sample). Please note that if you test too early for pregnancy, for example, just a few days after conception, then a negative result should not be regarded as conclusive. Different test kits have different sensitivity levels; therefore, read the instructions to determine when you should begin testing and ensure you follow instructions to optimize results.
Q: How long do I need to hold my urine? Is first morning urine the best sample?
Because home pregnancy tests detect hCG, it is best to collect urine samples containing the highest presence of the hCG hormone. Diluted samples (from drinking high volumes of water / frequent urination) are not recommended and can diminish test accuracy. Instead, first morning urine is considered the ideal sample as it contains the most concentrated presence of hCG. Otherwise, waiting several hours after last urinating to take a test.
Q: If the test band is faint, is the pregnancy test positive?
If the test is faint (in comparison to the control band), the test may be positive, though the presence of hCG in the woman's body - or urine sample - may be low. The presence of hCG doubles every two days in a pregnant woman. In cases where a faint test color band is present, it is recommended that you retake the test the following day using first morning urine. With most tests, a faint test band does indicate a positive result.
Q: How is it possible to receive a "False Positive" result on a pregnancy test?
False positive tests are rare - though there are instances and conditions where they can occur. For example, some tissues in a non-pregnant woman can produce hCG, though the levels are usually so low they are not detectable by home pregnancy tests (though our tests are the most sensitive on the market). Secondly, research indicates that half of all "conceptions" (fertilized eggs) do not go forward as developing pregnancy. Within this group, a proportion are recognized as "a chemical pregnancy" - a pregnancy in which there is a positive pregnancy test and no other signs or symptoms).
Moreover, a percentage of "false positive" pregnancy tests can be attributed to misinterpretation of results due to a failure to follow test instructions with precision. You should not rely on any positive result that does not show up within the time limit stated in the test instructions (see next question below).
Q: What if the test is negative after the minute reaction time, but becomes positive after an hour or more? Is this an evaporation line?
Do not attempt to interpret results after the test reaction time specified by the manufacturer. You should not rely on any positive result that does not show up within the time limit stated in the test instructions. All pregnancy test brands have the possibility of displaying an evaporation line.
Q: Can I be pregnant and not get a positive HPT (a False Negative result)?
False negative results are more common than false positives. A false negative result can stem from using a diluted urine sample and/or from taking a test too early in pregnancy. First morning urine contains the most concentrated presence of hCG - which makes it the ideal sample for pregnancy testing.
Additionally, at the same gestational stages, women produce quantitatively different levels of hCG - which means that the first indication of a positive result on a home pregnancy test may vary between women, despite similar gestational stage. If you suspect you are pregnant, you should see your doctor for a blood hCG test no matter what result you get from any home pregnancy test.
Q: Can fertility drugs or medication interfere with pregnancy test results?
The only medications that can cause a false positive on a home pregnancy test are those than contain hCG itself. If you are taking fertility medications with hCG - e.g. Novarel, Profasi, Pregnyl - please consult your doctor regarding appropriate times and circumstances for testing. Other fertility drugs and medications that do not contain hCG will not precipitate false positive results. Similarly, progesterone will not cause a false positive as well.
Q: How do I Interpret Pregnancy Test Results?
Once the reaction time of the test is complete, color bands will appear (or fail to appear) in the test region of the strip or midstream unit. All tests have a "control" color band (or color line) that indicates whether the test is working or not. The "test" color band indicates a positive or negative result (please refer to the graphic below). Given proper testing and interpretation procedure, a faint line in the test region may be read as a positive result, though it's a good idea to verify any result with an additional test 24-48 hours later (using first morning urine).

Read More About Pregnancy Tests:
> How Early Can I Begin Testing?
> Optimize: Tips for Pregnancy and Ovulation Testing
> Back to Pregnancy Testing
Comments
I had my last menstual period last Oct.31 until now Jan.18 my period did not come.My period sometimes not regular,seldom I missed 2 months,no period.I tried several times home pregnancy test lately every morning still result was negative.Is there any problem with me? Am I pregnant? I hope it's not.How long I will wait to confirm that im not really pregnant.im so worried pls I need your advice.thank you. More power.
My cycle is 34 days. My OPK test was positive on the 26th of Dec. so I broke out the donor sperm. I was exposed to have started my period on the 9th, five days late. When I was two days late I had my doctor run a blood test and it was neg. I have never missed a period. Could the blood test be wrong? I have had odd cramps for two weeks. Has anyone had a simular problem?
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I had my lmp on 12/14/09 and my partner and I had sex on 12/26/09 my cycles are 28 days long ..from what I hear thats abt 2 days prior to my ovalation date....could I be pregnant? I hope so and very anxious to know ? And how early can I take a preg test if so?
Thanx
i missed my period and 36th day ia have checked with preg test card the result was faintly positive now on 40th day i hv got my period ? now my doubt is will HCG level stiil remain in our body even after period and for how many days ?
I can't believe so many of you are having unprotected sex! If you don't want to get pregnant then PROTECT YOURSELF. GEESH!!!!
i have my last period on sep 28th. and the next period should be on nov 13th i expected. but till today i haven't got my period. my period is around 37 - 40 days. i start to worry. but these days i never feel nausea or vomiting or cramping.no spotted blood. no back aches. no constipation. but it confused me. but yesterday i came home with pregnancy test, it came out positive. i was using a container which is used for soap before. will it be a false-positive? am i pregnant? thanks
Soooo I have no idea if this means anything or not.... but I had unprotected sex probably about the time I was ovulating. A day before my expected period which was dec. 7th I started slightly spotting then got what I assumed was my period but then it suddenly stopped. My periods are very regular and are often pretty heavy the first couple of days. The period I had was some what heavy but not like normal. I have taken a few tests and all came up negitive. Its been 6 days since the weird period. How long should I wait to know for sure??
I can't remember the last day of my last period, but I believe I did have one last month, maybe around the beginning? Since I have been unsure of my last period, I have bought several pregnancy tests, every single one I have taken whether it be my first morning urine, or later in the day, they are all so far negative. But I still have not had my period, and I am beginning to get concerned. I know home pregnancy tests vary, and I just need to see what you might recommend. My periods are pretty irregular, sometimes I have them early in the month, and times later in the month, so I don't know if maybe I am just freaking out. Please let me know what you think. Thanks!
I had my period last Oct. 25 2009, and had unprotected sex on Nov. 12 & 13. Still no period. My periods are not the most regular, BUT there are more or less every 33-38 day. From what I know I don't have PCOS, definitely no cycts, and I've never tried to get pregnant before. Last week on Sunday, Nov 29, I took a HPC in the middle of the day after drinking plenty of water and urinating alot and the test came out negative. I now know I did the whole thing wrong. My BBT temperatures are high, I have the sudden urge that I'll be getting my period for the last week or so but no period. I feel a weird sensation in my uterus. I've never had this before. I'm not a real big carnivore but lately all I want to eat is meat. About a week ago I was feeling dizzy, nauseus and tired but in the last few days I've gain my energy back and feel much better now. Any advice out there?
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