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Houston Fertility Journal

Can Taking Certain Medications Result in a False Positive Pregnancy Test?

[fa icon="calendar"] Oct 1, 2018 11:02:23 AM / by Center of Reproductive Medicine   

Center of Reproductive Medicine

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Infertility is deeply frustrating, striking at the very core of who you are, what makes you human, and how you feel about your body. Many couples spend years taking pregnancy tests at the very first sign of a pregnancy or missed period. Some begin testing as soon as the woman ovulates. So the faint pink or blue line on a pregnancy test can spark jubilation, especially if you’ve previously seen dozens of negative tests. Yet false positives do happen. Medications can cause false positive pregnancy tests, turning your hope and jubilation into despondence and disappointment.

So are you at risk of getting a false positive pregnancy test? Here’s what you need to know.

Are You Sure it Was a False Positive?

It’s a painful scene: you and your partner sit down to take a pregnancy test, and are elated when the result is positive. But you’re anxious, so a few hours or a few days later, you take another test. It’s negative. You assume the first test was wrong. Or maybe you take another test, and another, and another…

It’s enough to drive the sanest, most patient person crazy.

First, a bit of good news: false negative pregnancy tests are much more common than false positives. Unless you take certain medications or have a disorder of your endocrine or reproductive system, it is very unlikely that you’ll ever have a false positive pregnancy test.

If you have a positive pregnancy test and then later get a negative pregnancy test, it could mean many things:

  • You had a false negative.
  • You were pregnant but had a miscarriage.
  • The second test was less sensitive than the first.
  • You had a false positive.
  • You are pregnant, but your pregnancy hormone levels are dropping, which usually means a miscarriage is imminent.

A false positive test is actually the least likely explanation here. So before you assume that a positive test followed by a negative test means you’re not pregnant, read on to understand. It’s important to see a doctor any time you have a positive pregnancy test to verify the results. Especially if there’s a subsequent negative pregnancy test, your doctor can help you determine which test was wrong and why the false test might have happened.

Why False Negatives Are More Common Than False Positives

False negatives are more likely than a false positive. The reason for this is that pregnancy tests work by detecting HCG. HCG is a hormone the body begins releasing in progressively larger amounts as the pregnancy develops. In the earliest days of pregnancy, HCG levels are very low—too low for most home pregnancy tests to detect.

Around the time that a woman misses her period, HCG levels are typically high enough for a home pregnancy test to detect them. But this varies from woman to woman, and depends on several factors, such as:

  • When the woman ovulated. If you miscalculate ovulation by a day or two, HCG may not yet be high enough.
  • How quickly HCG levels rise. Some women’s HCG rises more slowly than others. Sometimes, inadequate HCG levels are actually a factor in infertility. This can cause very early miscarriages that are mistaken for periods.
  • Whether a woman accurately calculated the date her period was due. The date of a woman’s period primarily depends on when she ovulated.

So if a pregnancy test is negative, it may become positive a few days later, as HCG levels get high enough to detect. This is why a false negative often turns into a very correct positive. So if you have a negative test followed by a positive test, a few days later, assume you’re pregnant and call the doctor.

Why False Positive Pregnancy Tests Happen

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A true false positive pregnancy test is a false positive that happens when a woman truly isn’t pregnant. Medications are the leading reason for true false positives because certain medications can change the way a woman’s endocrine system behaves. This can cause the body to release hormones that resemble HCG, or even to produce HCG.

In addition to medications, some other factors that can lead to false positive pregnant tests include:

Early miscarriage/chemical pregnancy

Miscarriage is common, affecting about 1 in 4 pregnancies. The miscarriage rate is highest in the earliest weeks of pregnancy, when genetic and physical anomalies are more likely to cause a pregnancy loss.

An early miscarriage can cause a positive pregnancy test that is followed by a negative pregnancy test. By the time you have a negative test, HCG levels are too low to detect that you were previously pregnant. This is known as a chemical pregnancy. A chemical pregnancy is a very early miscarriage, and warrants a conversation with a doctor—especially if you have had several miscarriages or chemical pregnancies.

Certain medical conditions

Medical conditions that affect the body’s hormone levels may cause the body to abnormally produce HCG, or hormones that resemble it. These same medical conditions can also lead to fertility difficulties. This is why it’s important to consult a fertility specialist if you have a serious or chronic illness.

Some medical conditions that can cause a false positive pregnancy test include:

  • Conditions that affect the thyroid or pituitary glands.
  • Cancers of any part of the endocrine system, such as the thyroid or pituitary gland.
  • Reproductive cancers of the ovaries, uterus, or cervix.
  • Gestational trophoblastic diseases, a group of medical conditions that cause abnormal growths in the cells from which a placenta normally grows.
  • Ovarian cysts.
  • Certain infections, especially of the kidneys or urinary tract.

In many cases, a woman will have other symptoms. She may mistake these symptoms, which are actually symptoms of an underlying disease, for pregnancy symptoms. This is yet another reason it’s so important to see a doctor for a false positive. For some women, a false positive pregnancy test is the first sign of a serious medical condition.

Evaporation line

Pregnancy tests work using a small strip of chemicals that detect HCG. When those chemicals encounter HCG, they change color. For the test to work, urine has to move across the strip of chemicals.

When a pregnancy test is left out for several minutes or hours, the strip of chemicals may slightly change color. Under certain lighting, this can look like a positive pregnancy test. This is why it’s important to carefully follow the test instructions. Reading a pregnancy test 10 minutes or longer after taking the test or allowing too much urine to get on the test can cause a so-called evaporation line that resembles a false positive pregnancy test.

Test malfunction or tampering

Very rarely, a pregnancy test can malfunction. The chemicals in the test might cause it to turn positive even in the absence of HCG. Or the test could even be tainted with HCG. In most cases, if the pregnancy test’s control line appears, the test is functioning fine. Even in this scenario, it’s possible for a pregnancy test to malfunction. This is why we recommend testing at least twice, with a pregnancy test from a different package. If you have two positive pregnancy tests, you are almost certainly pregnant.

Medication and False Positive Pregnancy Tests

It’s a cruel irony of fertility medicine: some of the medications designed to help you get pregnant are also drugs that can lead to the false hope of false positive pregnancy tests.

Fertility drugs that cause HCG are very likely to cause false positive pregnancy tests. So if you’re undergoing fertility treatment, ask your doctor if the drugs you are using are linked to false positive pregnancy tests.

In some cases, you may need to delay testing until 7-14 days after your last injection. In others, you might have to test at your doctor’s office.

Very rarely, some other drugs can cause a false positive pregnancy test. This happens when the drugs change the behavior of your endocrine system, which makes hormones. Some medications that may lead to a false positive include:

  • Cancer drugs, especially chemotherapy.
  • Immunosuppressant drugs.
  • Drugs that affect the thyroid or pituitary gland.

Surgery on the endocrine system, such as surgery on the thyroid or pituitary, may also affect pregnancy test results.

What to Do if You Take Medication That Can Cause False Positive Tests

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The infamous two-week wait can feel like torture. Each twinge and ache promises pregnancy, but you have no way of knowing what will come next. There’s no fast-forward button to testing day, and many people find that they spend endless hours perusing pregnancy and fertility forums or plugging data into calculators to estimate their odds of a pregnancy.

For people who know that their medications put them at risk of a false positive pregnancy test, the wait can be even more agonizing. You may have to wait longer, or even schedule an appointment with your doctor before you can get an answer.

That doesn’t mean you’re powerless. There are a lot of things you can do to manage the wait.

Some strategies that may help include:

  • Charting your monthly cycle. Charting your cycle, including your basal body temperature, provides lots of important information about your fertility. This information may even help your doctor rule in or out certain causes of infertility. Your chart can even provide some early hints that you’re pregnant.
  • Talking to your doctor about medication options and timing testing. There might be an alternative drug that doesn’t contain HCG. Or you might be able to avoid a false positive test by testing on a certain day.
  • Joining an infertility support group. One of the biggest challenges when you take a drug that contains HCG is that you have to wait longer than most people do to find out if you are pregnant. An infertility support group, either online or in person, may be able to help. To find a local support group, click here.
  • Prioritizing your health. Consider behaving as if you are already pregnant. This gives your baby the best chance of growing and developing in a healthy environment, even before you know you are pregnant. Take a prenatal vitamin. Exercise. Avoid alcohol. Eat a balanced, healthy diet. You’ll feel physically and emotionally better if you are healthy. You’ll also improve your chances of getting and staying pregnant.
  • Finding a distraction. Spending all your time googling pregnancy symptoms is a recipe for losing your mind. Find something else to do. Go for a run. Go out with friends. Read a book. Make a meal. By finding meaning in things that aren’t pregnancy-related, you remind yourself that pregnancy isn’t the only thing in your life that matters.
  • Asking your doctor lots of questions. Your doctor can give you a detailed overview of your diagnosis and what it means. This can help you understand your pregnancy odds, make intelligent decisions about your health, and set reasonable expectations for each cycle.
  • Talking to your partner. Women in particular sometimes think they have to go it alone. This is both of your problem. Don’t suffer in silence. Lean on your partner, and find ways to find joy in one another. A vacation, a date night, a romantic evening at home, and an adventurous day taken off of work can all help make the wait feel manageable.

You Don’t Have to Go it Alone

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Infertility comes with a complex cornucopia of emotions—denial, anger, shame, depression. It can tear families apart, and upend healthy relationships. It doesn’t have to. Infertility, though frustrating, is common. One in eight couples struggle with infertility. You are not alone, even if you feel like you are.

The Texas Center of Reproductive Medicine specializes in helping people from all walks of life with infertility. We offer specialist care, comprehensive diagnosis, and a greater chance of a pregnancy than you will get with a gynecologist or family physician.

If you’re under 35 and have tried longer than a year to get pregnant, over 35 and have tried longer than six months, or you have a chronic medical condition, it’s time to seek help. We can help you navigate the stormy waters of infertility, offer resources that help you manage the frustration and pain, and give you the best possible shot of a successful, happy, healthy pregnancy. If you’re ready to get off the gerbil wheel of frustration, we’re ready to help. Give us a call today!

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Topics: Pregnancy, Signs of Infertility, Health

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