Can a yeast infection cause false positives on pregnancy test

Microbiology

Notes

• The routine pregnancy test has a sensitivity of 25 IU/L.
• The test will become positive 7 - 10 days after conception and by the time of the first missed period levels frequently exceed 100 IU/L.
• Dilute urine samples (i.e. with a low specific gravity) may not contain a representative levels of hCG, potentially leading to a false negative result. If pregnancy is suspected, collect an early morning (first) urine sample and retest.
• A very early pregnancy with low levels of hCG can give a negative result. If pregnancy is suspected a first morning urine sample taken at least 48 hours from the date of this specimen may be of value.
• hCG levels may remain detectable for several weeks after normal delivery, delivery by caesarian section, spontaneous abortion or therapeutic abortion.
• Elevated levels of hCG can be caused by a number of conditions other than pregnancy, including trophoblastic disease and some non-trophoblastic neoplasms such as testicular tumours, seminoma, choriocarcinoma, germ cell tumours, hydatiform mole formation, teratoma with elements of choriocarcinoma and islet cell tumour. Therefore, the presence of hCG in urine should not be used to diagnose pregnancy unles these conditions have been ruled out.
• Serious urinary tract infections (with high levels of WBC, RBC and nitrite) can occasionally cause a false positive pregnancy test result.
• Ectopic pregnancies typically produce lower levels of hCG than normal preganancies. This will be accentuated by the dilution effect in urine. Therefore, a negative result cannot reliably exclude ectopic pregnancy.
• Fertility treatments based on hCG may cause false positive results.

Sample requirements

Urine.

The first urine specimen of the morning is ideal (more dilute urine samples may not contain representative levels of hCG).

30mL sterile Universal

Bottles with boric acid have not been validated for this test and will therefore not be accepted.

Required information

• Date of LMP.
• History of ectopic pregnancy or loss of established pregnancy.

Storage/transport

Transport to the lab as soon as possible at ambient temperature.

If transport is delayed, store at 2 - 8°C for up to 48 hours.

Turnaround time

1 - 2 days

No matter what, taking a pregnancy test can be an emotional roller coaster. When it comes to getting a false positive pregnancy test result, the experience can be deeply upsetting, particularly for anyone who has had a difficult time getting pregnant or is actively hoping to get pregnant (or both). The hope that comes with seeing that positive sign crashing down as you realize it was a false positive pregnancy test? It's a uniquely devastating emotion. 

Of course, getting a false positive pregnancy test when you’re actively trying not to get pregnant can be just as horrible. Yup, you could probably do without the panicked verification trip to the ob-gyn, just to learn there was nothing to stress over. 

Thankfully, experts note that false positive pregnancy tests are rare. Unfortunately, though, they can happen. Here are some of the most common causes of a false positive pregnancy test, along with some additional information that can help you put it all into context.

First, what is a pregnancy test?

Let's start with the absolute basics just to make sure we're all on the same page. A pregnancy test tells you if you’re pregnant or not. That's simple enough to understand. But it's understandable if you're a little fuzzy on the details of what these devices actually look for to identify a pregnancy.

At-home pregnancy tests check for the hormone hCG. HCG is short for human chorionic gonadotropin, which the body creates during pregnancy. Right after a fertilized egg attaches to the uterine lining, the placenta then forms and starts producing hCG1. A blood test can detect hCG about nine days after conception, and a urine test can detect it 12 to 14 days after conception, according to the Cleveland Clinic, although it varies—some especially sensitive urine tests can detect a pregnancy even earlier. A person’s hCG level typically doubles every 72 hours through 8 to 11 weeks of pregnancy. Then it remains consistent and starts to go down after delivery.

Back to top.

How does a pregnancy test work?

An at-home pregnancy test is designed to find hCG in pee2. If the hormone is present, it triggers a chemical reaction and the test signals that you're pregnant. If hCG is not present, the test will say you aren't pregnant. Many tests use two lines to mean you’re pregnant and one line to mean you’re not—but it depends on the test brand. Some tests use plus and minus signs. Some digital pregnancy tests have a screen that plainly reads "pregnant" or "not pregnant." Which can save you some “Is that one line or two?!” squinting, at least.

Seems simple, right? As Ina Garten would say, "How easy is that?" Typically, pretty easy. Most at-home pregnancy tests claim to be about 99% accurate3. Ultrasounds typically can't detect a pregnancy until a little later in your pregnancy and that's why at-home tests are so useful. But, sometimes, other elements can mess with a pregnancy test's results and tell you you’re pregnant when you’re really not. 

Back to top.

What can cause a false positive pregnancy test?

Here are the most likely reasons you may end up with a false positive pregnancy test:

1. You let the test sit too long before looking.

If you take a standard pregnancy test with line indicators, it's important to check the results according to the specific instruction of the test. If you let it sit too long before reading the results, urine on the test can evaporate and make it look like you have two lines instead of just one. "Oftentimes people will see evaporation lines as urine starts to evaporate off the test," Jamil Abdur-Rahman, M.D., board-certified ob-gyn, tells SELF. That might cause the test to look like it has a faint second line—making it positive—but it really only has one.

The best way to avoid this: Read the pregnancy test's directions and follow them exactly. The popular pregnancy test brand First Response, for example, instructs users to wait three minutes after taking the test, then read it as soon as possible4.

2. The pregnancy test is expired.

The second most common reason Dr. Abdur-Rahman's patients get false positives is because the test is expired, he says. When a test is past its expiration date, the chemical that detects hCG doesn't always work as it should, and you’re more likely to get a misread. "The test can expire and the chance of having a false positive increases," Dr. Abdur-Rahman says.

3. You’re on fertility medications that raise hCG levels.

If you take a pregnancy test too soon after taking a fertility drug that contains hCG—like some injections that are often part of in vitro fertilization—you could get a false positive.

What infections can cause a false positive pregnancy test?

Can a UTI or yeast infection cause a false positive pregnancy test?

Can yeast infection cause a false positive?

Can I use infection come up as a positive for pregnancy test?

What else could cause a positive pregnancy test?

Is a yeast infection early signs of pregnancy?