Most women of child-bearing age are very familiar with the home pregnancy test. Home pregnancy test strips work by detecting the pregnancy hormone human chorionic gonadotropin (HCG) in the woman’s urine. The further along you are in the pregnancy, the higher the level of HCG. Most commercially available pregnancy tests claim to be 99% accurate but what if the pregnancy test is expired? Can you rely on the result of the expired pregnancy test?
Do Pregnancy Tests Expire?
The answer to this question is yes. The test strip contains a special chemical that reacts with a hormone (HCG) which is excreted into the urine only if that person is pregnant. The test will be expired and no longer valid when this chemical is ineffective at detecting this pregnancy hormone in your urine. Manufacturers can only be sure of that chemical’s shelf-life and how it will behave in the presence or absence of that pregnancy hormone up to that specific expiration date.
When Do Pregnancy Tests Expire?
Most commercially available pregnancy tests have a shelf-life of between 2-3 years after manufacture. All manufacturers print an expiration date clearly visible on the box or outer packaging of the test strip. Always check the expiration date on the box or the outer packaging before you use it to avoid any false results. To minimize any stress and doubt, rather use a test that is well before the expiry date. If you can, it would be better to buy a test strip that has been manufactured fairly close to the time you want to use it.
Are Expired Pregnancy Tests Accurate?
There is no way to say that an expired test will absolutely give a false result, but it can't be reliable, either. Apart from a laboratory setting, you cannot determine if the chemical on the pregnancy test strip is inert or still active after the expiry date.
Do not bother using an expired test strip. If you’re buying multiple tests, rather take the extra time to examine several tests and purchase only those with expiration dates as far off as possible.
Other Situations That Give You False Negative/Positive Results
Although these pregnancy tests are pivotal in many women’s lives, they are not always accurate and can give false results. Apart from the expired pregnancy test, there are certain conditions when a false reading is still the result. This can happen in the following situations:
1. Being Too Eager to Test
You may be taking the test too early. There may not be enough HCG in your urine to be detected by the test strip. About 3% of pregnant women may still show a false negative after the first missed period because their levels of HCG are not high enough. These women should repeat the test after a few days to allow the HCG levels to increase. Due to the rapidly increasing levels of HCG in a pregnant woman, a negative result about one week after a missed period is fairly accurate.
2. Incorrect Testing Technique
Read the manufacturer user instructions carefully to ensure using the test correctly. It is usually advised to test with the first passing of urine in the morning after you get up when the concentration of HCG will be the highest at that time. Take note of whether the test is a midstream test or do you have to dip the stick into the urine. Most tests take up to 3 minutes to read the results. Reading the results on some tests have to be done within 10 minutes otherwise the result is invalid.
3. Fertility Drugs
Some fertility drugs contain HCG which causes a false positive result.
4. Medical Conditions
Some medical conditions cause your body to produce HCG in the absence of a pregnancy—this also shows up as a false positive.
5. Miscarriage
Detectable HCG levels are still present in the urine even after the pregnancy has ended in a miscarriage. It may take weeks for the HCG levels to drop.
6. Ectopic Pregnancy
Sometimes the fertilized egg doesn’t implant into the uterus but elsewhere like the fallopian tubes. It is called an ectopic pregnancy. This type of pregnancy is not viable and the embryo will not develop. An ectopic pregnancy will show normal increases in HCG which will lead to a false positive.
7. Chemical Pregnancy
Sometimes a fertilized egg implants into the uterus but for some reason stops developing. There will still enough HCG to be detected by a test strip which can lead to a false positive.
8. Misreading the Test
Sometimes when the urine evaporates from the test strip, it leaves a colorless line behind on the strip window that can be mistaken as a positive result. Remember that the tests are designed to change color in the case of a positive result. It is very important to note that once a test is used, regardless of the result, it should be discarded and never reused, just like expired pregnancy tests.
9. Irregular Cycles
Many women are unable to predict their next period due to irregular menstrual cycles. These women cannot say with certainty when they are missing a period. They should retest after a few days.