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We are often asked how a woman can tell if she is pregnant. In a previous blog post, I detailed the most common early signs of pregnancy. In this post, I will describe the different types of pregnancy tests available, either those performed at home or at the doctor’s clinic. To simplify, I will classify the tests as:
- Home Pregnancy Tests
- Clinical Urine Test
- Blood Test
1. Home Pregnancy Tests
Home pregnancy tests (HPT) are available in digital and standard stick forms. Digital tests can be used up to 6 days before your missed period while the standard stick test can be used up to 4 days before your missed period. Please, be aware that, if you test too early, you could get a false negative result. A false negative result means that you are pregnant but the test says the opposite.
Ideally, you should test first thing in the morning because your urine and hormone levels will be more concentrated then. However, this is not a requirement for the test to be accurate. Make sure you place the stick in midstream urine pointing downward, then lay it flat, and give it 3 to 5 minutes to work. Alternatively, you may collect a sample of your urine in a clean, dry container. Dip just the absorbent tip into your collected urine sample for 20 seconds only. After sampling, keep the absorbent tip pointing downward. Never hold the test stick with the absorbent tip pointing upward.
If the result is negative, try again in a few days if your period has not yet started. If you get a faint line, chances are you’re indeed pregnant.
How do they work? All home pregnancy tests work by measuring a hormone known as human chorionic gonadotropin (hCG). This hormone is released by the developing placenta, and traces can be found in the urine after the embryo implants in the uterus. In a 28 day cycle with ovulation occurring at day 14, hCG can be detected in urine in minute quantities around day 23, or 5 days before the expected menstruation. The hormone concentration doubles approximately every 2 days and peaks between 7-12 weeks after the first day of the last menstrual period. Pregnancy tests contain a fiber strip coated in certain antibodies that react with the hCG and a pigment indicator to produce those positive or negative lines displayed in the standard stick test window.
Digital or non-digital? Digital tests can be used earlier and are more sensitive and faster to provide the result than standard stick tests. Some women also prefer digital tests because they clearly flash the results – “pregnant” or “not pregnant” onto the LCD screen on the indicator stick. Bear in mind that digital tests are more expensive (about $10 vs standard stick tests for about $5 dollars or even less) and you may need a few of them. First ResponseTM has a new digital test that connects via Bluetooth to a mobile App at around $20.
Accuracy. Digital tests are accurate approximately 51% of the time when used 4 days before your expected period, 82% of the time when used 3 days before your expected period, 90% of the time when used 2 days before your expected period, 95% of the time when used 1 day before your expected period, and 99% on the day of your expected period. Standard stick tests are considered to be 97% accurate on the day of your expected period.
Expiration date. All the available pregnancy tests normally last for anywhere between two to three years after production. Given the importance of what you are trying to accomplish, taking a test using an expired pregnancy test is as good as not taking one in the first place.
2. Clinical Urine Test
A urine test can also be performed at a doctor’s office. The urine tests used at a doctor’s office are not commercially available in pharmacies but they are based on the same principle of hCG detection as the HPT and are, essentially, equally accurate. The main difference is that, with the help of a professional, you may be able to eliminate any potential errors that could affect the accuracy of the test. Bear in mind that a clinical urine test will probably cost more than an HPT, depending on your co-payments.
3. Blood (Serum) Tests
These tests are taken at a doctor’s office. A laboratory tests a woman’s blood to detect the presence of hCG. Blood tests can detect hCG earlier than urine tests. Blood tests tend to be more expensive than home tests and the results take longer. There are two types of pregnancy blood tests.
Qualitative hCG Blood Test: This test checks to see if there is any hCG being produced in the body. It gives a simple yes or no answer as to whether or not you are pregnant. Doctors often order these tests to confirm pregnancy as early as 10 days after a missed period. However, some of these tests can detect hCG much earlier.
Quantitative Beta hCG Blood Test: This is the most accurate of all pregnancy tests. It measures the specific level of hCG in the blood. Because these pregnancy tests can measure the concentration of hCG, they may be helpful in tracking any problems during pregnancy. They may also (in combination with other tests) be used to rule out a tubal (ectopic) pregnancy or to monitor a woman after a miscarriage when hCG levels fall rapidly. When your lab test comes back, your doctor will tell you what your hCG levels are. These levels are measured in milli-international units of hCG hormone per milliliter of blood (mIU/ml). Normal hCG levels in non-pregnant women are less than 5.0 mIU/ml. If your hCG levels are outside of the normal range, it could mean a variety of things. Your doctor will help you interpret the results.
The out-of-pocket expense for a blood pregnancy test will vary depending on the clinic you choose and the type of insurance you have. You should expect to pay up to about $75 for this service. And, if the results are uncertain, a re-test will be required a few days later, which will in most cases incur an additional fee.
Can a blood test be negative while in reality I am pregnant (false negative)? Can a blood test be positive when in reality I am not pregnant (false negative)? Read this Pregistry blog post for the answers.