Here's something your sex ed course might’ve skipped: the 101 on pregnancy tests. It might sound simple on the surface, but it brings up a lot of questions. For instance, what's the best time of day to take a pregnancy test? What if you see a faint line on your pregnancy test? Do they expire? We’ve got the answers, thanks to Dr. Julia Simon, an OB-GYN and assistant professor of Obstetrics and Gynecology at the University of Chicago and Dr. Pamela Berens, professor of Obstetrics and Gynecology at McGovern Medical School at UTHealth Houston.
Are there different kinds of pregnancy tests?
There are two main types of pregnancy tests: urine and blood tests. Sex ed recap: Your body produces a hormone called human chorionic gonadotropin (hCG) after a fertilized egg is implanted in the uterus. The tests analyze your blood or urine for the presence (and level) of that hormone.
Your doctor will order a blood/serum test and this will be performed at a lab. These tests are around 99% accurate and can detect even small amounts of HCG. They’re sometimes used to confirm the results of an at-home test, or if you’re facing symptoms such as bleeding or abdominal pain, which are also symptoms of a miscarriage. An at-home test will usually suffice, says Dr. Berens.
There are three types of at-home urine pregnancy tests to choose from:
Midstream: Urinating directly on the test stick (like First Response or Clear Blue)
Cassette: Urinating into a cup, then applying drops of urine to the test stick (like Accu-Test or Equate First Signal One-Step)
Strip: Urinating into a cup, then putting the test strip directly into the urine (like First Response Pregnancy Comfort Check or Easy @ Home)
Most of these tests are similar and can usually detect a pregnancy a week after a missed period with 97-99% accuracy, says Dr. Berens. It comes down to what type of test you would prefer to take and which method you’re most comfortable with.
How much is a pregnancy test?
A pregnancy test from the drugstore can cost around $8 to $20. If you take multiple tests, it can really add up. Good news if you have an FSA or HSA account: OTC pregnancy tests are eligible for both.
Blood tests may cost around $50 or more without insurance. If you do have insurance, it may be covered, since marketplace insurance companies are required to cover pregnancy care. That said, call up your insurance company to make sure.
How soon will a pregnancy test read positive?
Experts say the soonest you should take a test is two weeks after unprotected sex. That’s why it’s often called the two week wait. It’s just enough time for your body to build up enough hCG to be detected. Taking a pregnancy test too soon can increase your chances of a false negative.
So you can get a false negative pregnancy test result?
It can happen. Aside from not waiting long enough after having unprotected sex, some of the most common reasons are because…
You didn’t check the pregnancy test box.
Before you start, you’ll want to check a few things on the test box. One is the expiration date, because yes, pregnancy tests do expire. They usually last one to three years after manufacturing. Over time, the antibodies that coat at-home pregnancy tests begin to lose effectiveness and evaporate. The second thing to check is how to conduct the test and how long to wait for results. One test may tell you to wait at least a minute, others might tell you to wait longer.
You took the test later in the day or at night.
Taking the test in the morning will give you the most accurate results, says Dr. Berens. Waiting until later in the day or drinking a lot of liquid before testing can dilute your urine and affect the test’s ability to detect hCG.
You're experiencing a cryptic pregnancy.
It’s when someone is pregnant, but doesn’t realize it until far along into the pregnancy (or until they go into labor). It’s extremely rare, but can happen if you don’t experience significant pregnancy symptoms, have irregular periods, or don’t develop an obvious bump.
Got it. What does a faint line on a pregnancy test mean?
No matter how faint the second line is, it typically means you’re pregnant. It could just mean you're early in your pregnancy. If you take the test again in a few days, you should see a stronger line. It means your body has had more time to build up more of the hCG hormone.
That said, be on the lookout if you continue to see a faint line on additional tests. If you see it again, if you’re having bleeding or lower abdominal pain, or if your period is late by a few weeks, it may also be a sign of an abnormal pregnancy. In those cases, you should contact your health care provider right away, says Dr. Berens.
A faint line can also be a sign of a false positive pregnancy test. They happen less than 1% of the time. If it does happen, it may be because the pregnancy was lost soon after the fertilized egg implanted in the uterus. Which may also be called a chemical pregnancy. Or, because you took a pregnancy test after taking fertility medication that contains hCG. If you aren't sure about your results, follow up with your doctor to confirm.
One plastic stick can have a major impact on your life. So be sure to follow the instructions carefully, check the expiration date, and if you're trying to conceive, take the test within the right time window. All of this will help give you the most accurate result. If you’re not sure about the results, schedule an appointment with your OB-GYN.
Updated on Apr. 7 to reflect new information.
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