Pregnancy

Understanding Pregnancy Tests

An Overview of Home Pregnancy Tests

Home pregnancy tests are sold almost everywhere. You can find them in most stores, from your major retailers to your grocery store, convenience store, and even discount stores.

Simply having pregnancy tests readily accessible, however, doesn't help you decide whether or not you should take a pregnancy test, nor does it tell you whether or not you should believe the results. So, how do these things work?

And which one should you take to get the most accurate answer? Yes, there are a lot of questions about home pregnancy test kits. Here are some answers.

How Do Home Pregnancy Test Kits Work?

To start by talking about how a home pregnancy test kit works, you need to understand the very basics of early pregnancy. Once a sperm and egg meet, they begin to rapidly transform into a blastocyst, a small cluster of cells.

These cells continue to divide and make more cells, though it takes close to two weeks for the body to even know that any of this is happening. When your body senses the pregnancy, your period is canceled and doesn't start.

The pregnancy will begin to produce a hormone called human chorionic gonadotropin (hCG). This is the pregnancy hormone, and it is what a pregnancy test is looking for to say whether or not you are pregnant. Home pregnancy tests look for hCG in your urine, as the hormone is excreted or passed when you use the bathroom. At first, this happens in very small quantities, but the further along in pregnancy you are, the more hCG can be detected.

Most home pregnancy test kits work by having a slip of paper that reacts by changing color when hCG is present. Or in the case of digital pregnancy tests, when hCG is present, the "pregnant" sign lights up, but it's still doing so because the pregnancy test detected hCG.

How Do Home Pregnancy Tests Work Differently From a Pregnancy Test at the Doctor?

The short answer to this question is that for urine tests, the home pregnancy test is not very different than the one you get at your doctor or midwife's office. A test kit that you buy may come with more packaging and more detailed instructions, like how to collect urine, but it is essentially the same kit that you will find in any medical office.

Now, there are also blood pregnancy tests. A blood pregnancy test is also looking for the hormone hCG, though it is screening your blood. These are ordered by your doctor or midwife. It can be ordered in two varieties: quantitative (measures how much hCG) or qualitative (measures existing hCG, if any).

A qualitative blood test is basically the same as a urine test—it determines whether or not there is hCG. Though a blood test can usually find slightly smaller levels of hCG, so it can usually help you find out a day or two sooner. 

A quantitative blood pregnancy test will actually give a number, a measurement of how much hCG is found. This number is given typically in mIU/ml (milli-international units per milliliter). This number can be used in a number of ways. One way is that a certain number can correlate to the length of your pregnancy. This may be helpful in dating a pregnancy.

A serial hCG test, meaning more than one, taken a couple of days apart, can not only give an estimated length of pregnancy, but often tell a bit about the health of a pregnancy. For example, if your hCG numbers are nearly doubling after two days, this indicates that a pregnancy is healthy for the time being. An hCG that is not rising quickly enough or is actually falling, may indicate a miscarriage, early pregnancy loss, or even an ectopic pregnancy.

Blood pregnancy tests are generally only done for women who are having problems in their pregnancy or require special testing. Even if you go to your doctor's office for a pregnancy test, the vast majority of them will offer you a urine test.

What Should I Look for in a Home Pregnancy Test?

So, when you want to buy a pregnancy test, you will have many options. You will need to decide what you want out of the pregnancy test and when you want it. The questions you need to ask before deciding which home pregnancy test you should buy will be:

  • When is/was my period due?
  • How confident am I in my ability to read a pregnancy test?
  • How confident am I in my ability to perform a pregnancy test?
  • Have I ever taken a pregnancy test before?
  • Will I need more than one pregnancy test? (Be honest with yourself!)
  • Am I taking any medications containing hCG? (Usually only if you are in treatment for fertility issues.)

If your period is not yet due, there are pregnancy tests on the market that say they will tell you if you are pregnant or not.

They usually cost a bit more than your standard home pregnancy test kit, but they can only tell you that hCG is present. If it is, you are pregnant. If it is not found, it may be that you are not pregnant, or it may be that it is simply too early to test.

If you are worried about your ability to read a pregnancy test, you may wish to consider a digital pregnancy test. This is a simple readout that says Not Pregnant or Pregnant. There is no guessing as to whether or not you see a line, or if a line you see is an evaporation line.

If you are worried about your ability to take a pregnancy test, you may wish to spend a bit more on a pregnancy test that comes with great instructions and a toll-free number that you can call with questions. The box will tell you what is inside the kit, including instructions, and information on the collection of your urine. (Some tests have you urinate in a cup and test with that urine, while others have you "pee on a stick" to catch the urine.) How you collect the urine can alter how you feel about your ability to take the test. (Though you can always use the catch method, even if it instructs you to use a stream of urine.) Having the toll-free number might encourage you.

If you have taken a pregnancy test before or you're really confident in your abilities, the cheaper pregnancy tests are very accurate and work just as well as their more expensive counterparts. Some people are leery of spending a dollar on a pregnancy test, or less in bulk, but what you're missing is detailed instructions and the bulk of the packaging. You may also not have access to a toll-free number. If you want to test multiple times, you may also want to go with the less expensive option. This is great if you are testing before your period is due.

No matter which brand of test or type of home pregnancy test you chose, be sure that you check the expiration date on the pregnancy test box. The biggest error people get when testing for pregnancy is using expired pregnancy tests. If you are buying your pregnancy tests online, be sure that you know the tests you're purchasing are not expired or about to expire (for bulk purchases).

How Much Will a Pregnancy Test Cost?

Pregnancy test kits vary from just under a dollar for bulk purchases without lots of packaging to over $25 for a single pregnancy test, typically a digital, early pregnancy test with lots of packaging and a toll-free number. How much you pay for your test is not typically correlated with how well it works. Even if you decide to go for a test with more instructions and support, you can still save a lot of money by purchasing test kits that have multiple pregnancy tests included. Even if you don't take both this pregnancy, you can usually save the other test for a couple of years. (Check the expiration date!)

If you can't spend the money on a home pregnancy test, there are places to get a free pregnancy test as well. Be sure you know who is doing the test and what their credentials and motives are for testing.

When Should I Take a Pregnancy Test?

Taking a pregnancy test is a personal choice. Some people want to put it off as long as they can, meaning their period is two weeks late before they even think about it. Other people are charting ovulation and want to take a pregnancy test about 12 hours after they think they got pregnant. In reality, a blood test, at the earliest, will detect miniscule amounts of hCG about seven to 10 days after conception (not ovulation), and a urine or home pregnancy test kit will begin to see some positives 12 to 14 days after conception. 

The real question is why do you need to know? If you need to know because of an issue with a medication you need or a medication you need to stop taking, talking to your doctor or midwife would be the most helpful in determining how and when to take a pregnancy test. A home pregnancy test may not be your best option in this case.

If you are just really anxious and want to know, you can use an early home pregnancy test kit, though I would not start until at least 12 days post-ovulation, though that may also not be helpful because a negative pregnancy test may simply mean it's a bit too early and multiple tests may be needed. In this case, I always tell people to assume a positive is a positive and that a negative is an "I don't know yet" until your period starts or you have a positive. Act pregnant until you know you're not.

How Do I Take a Home Pregnancy Test?

The instructions for taking a home pregnancy test are all pretty similar. You will want to follow any instructions as far as timing the test that come with your pregnancy test kit. 

You will probably get better results from using first morning urine (fmu), or urine after you have not urinated for several hours, in the case of shift workers. This allows you to have more urine built up to better aid in detection. Later in pregnancy, this won't matter as most tests detect very small amounts of hCG, around 20-25 mIU. 

Start by gathering up everything you will need. Your test kit, something with which to keep time (phone or watch), instructions, and a cup, if you are collecting the urine. Wash your hands and either collect the urine in a clean cup, which may be provided or you can use small disposable cups, or open the test kit and remove any shields and urinate on the place where indicated on the test (sometimes you have to move your hand around to catch the stream). If you didn't do the stream method, place the appropriate number of drops on the test or dip the test stick/strip into the cup for five seconds or other time, if indicated. 

Lay the test kit flat and note the time. Most test run in about two minutes. It can be dangerous to read the test prior to this because some will look positive as the test is being performed. I usually encourage you to set a timer and walk off or otherwise occupy yourself for 2-5 minutes, depending on the test. Digital tests can be read easily. A strip test will have two lines, either parallel or in the form of a plus for pregnant, or one line vertical (instead of two lines) or a negative sign instead of a plus sign (check the instructions on how to read the test).

Do not read the test later than instructed, particularly the next day as it is not accurate. Typically any color change in the area of the second line would indicate the presence of hCG and therefore a positive test. The two lines do not need to be the same shade for the test to be positive.

When Should I Repeat a Pregnancy Test?

You should repeat a test that is negative prior to the start of your period. It is best to wait at least two days to test to give your body a chance to build up to the hCG needed to turn the test positive. You should also repeat it if your period does not start after a couple of days to a week.

Some people simply enjoy the pregnancy testing process. It can be hard to believe that you are pregnant. It's a life-changing event. All you have is a little piece of color changing paper telling you that a baby is growing. You want to see that again—maybe it was wrong the first time. Sometimes this provides you with comfort. Sometimes it only scares you. Know which camp you fall into before you test again.

If you have a positive test and test later that day to prove it to yourself and the test is negative, you will panic. Sure, you could have had a chemical pregnancy, or it could just be later in the day and your hCG levels in your urine are down. How will you cope?

What Should I Do With the Results of a Pregnancy Test?

If you have a positive pregnancy test, you will want to schedule an appointment with the doctor or midwife of your choice. They will guide you further in how to care for your pregnancy. They will also be the person with whom you can share concerns or ask questions, even prior to your appointment. 

Many women are surprised at how long it seems to take to get in to see a doctor or midwife in early pregnancy. This is not uncommon. It can be normal to not be seen until after you would normally be eight weeks pregnant or have missed a second period. If this concerns you, speak up. Perhaps you have a medical concern that needs to be addressed sooner. Don't hesitate to ask for something different. If you aren't being heard, consider looking elsewhere for your care. Most offices offer, at the very least, a nurse call line.

If your pregnancy test was negative, you will want to wait and repeat it. Most pregnancy test kit instructions recommend waiting at least a week to repeat the test. If the test is still negative, you will want to schedule an appointment for a physical exam. There may be any number of reasons why your pregnancy test is negative and you haven't started your period.

Sources:

Bryant AG, Narasimhan S, Bryant-Comstock K, Levi EE. "Crisis pregnancy center websites: information, misinformation and disinformation." Contraception. 2014 Dec 31;90(6):601-605. 

Nerenz RD, Butch AW, Woldemariam GA, Yarbrough ML, Grenache DG, Gronowski AM. Clin Biochem. 2015 Nov 2. pii: S0009-9120(15)00507-X. doi: 10.1016/j.clinbiochem.2015.10.020. [Epub ahead of print] Estimating the hCGβcf in urine during pregnancy.

Pregnancy Tests. Any Lab Test Now. https://www.anylabtestnow.com/tests/pregnancy-test/ 

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