Why Pregnant People Can Get a False Positive HIV Test

Testing for HIV during pregnancy is a routine part of prenatal care, which bumps up the chance you might get a false-positive result. Experts explain why that can happen.

Nurse getting blood from on a pregnant woman
Photo: bluecinema/Getty Images

Growing a human for nine months can be stressful for many reasons—one of them being all the testing and blood work that is recommended throughout pregnancy. And even though certain exams and labs are par for the course, they can lead to unexpectedly nerve-racking moments. That's what one expectant mom in the Baby Bumps subreddit contended with, sharing that she received what she suspected was a false positive on her routine first-trimester HIV test.

The original poster (OP) wrote, "I had first-trimester blood work done last week to confirm pregnancy, etc., and got a voice message from my doctor to make an urgent appointment. I go in today as she says one of the tests came back positive for HIV. I'm just in complete shock/disbelief. She reassured me that it's likely to be other antibodies reacting to the test and that I'll need follow-up blood work to confirm."

The OP noted that she had seen other people in the subreddit get false positives, so she wanted to share her situation with the community.

Can Pregnancy Cause a False Positive HIV Test?

So, can pregnancy cause a false positive HIV test? Not exactly, but false positives do happen. Experts say pregnant people can experience false positives simply because they're tested more often (once in the first trimester and once in the third) than the general population.

Although uncommon, false-positive results do occur less than 2% of the time, according to the Centers for Disease Control and Prevention (CDC). But depending on the type of the test, false positives are experienced more often in pregnant people, notes Jamie Lipeles, D.O., OB-GYN and founder of Marina OB-GYN in Marina del Rey, California.

At the same time, the screening test used for HIV is not always precise, says Felice Gersh, M.D., OB-GYN, founder of the Integrative Medical Group of Irvine in California, and the author of PCOS SOS Fertility Fast Track. "The screening test used measures antibodies, but there is a possibility that other substances in the [person's] body will react and result in a false-positive test," says Dr. Gersh. "When the screening test of a pregnant [person] returns a positive result, a different type of test, called the Western blot (WB), is run as the confirmatory test."

Possible Causes of False-Positive HIV Test

The following circumstances, viruses, and conditions are believed to increase the likelihood of a false-positive HIV test, according to Dr. Lipeles:

  • Administration of the flu vaccine (the CDC recommends that all pregnant people get the vaccine during pregnancy)
  • Presence of HLA-DR antibodies in those who've been pregnant before
  • Presence of rheumatoid factor
  • Positive RPR test (screening for syphilis)
  • Increased antibodies in your blood, or hypergammaglobulinemia, which may be caused by an infection or multiple myeloma
  • Autoimmune hepatitis

Meanwhile, additional studies are ongoing to determine if a pregnancy-specific factor could potentially increase the incidence of false-positive HIV tests, notes Dr. Lipeles. That's heartening to hear, given that, as other researchers have pointed out, efforts should be made to minimize undue stress for pregnant people.

The Redditor's Story Highlights Why False Positives Are So Stressful

The OP of the Reddit post is a perfect example of the stress a false-positive test could create. She said her doctor reassured her that HIV is a manageable disease, life expectancy is high with proper medication, and the risk of transmitting the disease to the baby was low to none, factoring in meds. But the expectant mom wrote, "I just nodded along in shock cuz I couldn't process what she was saying."

Other Redditors pointed out that the stigma of HIV is still a significant issue. "HIV carries such a huge (and nowadays completely undeserved) stigma," one said. "What I wanted to say is that if it is positive, it's not your fault. Anyone with the slightest understanding of the virus knows this, and it says nothing about who you are as a person."

Another Redditor, who identified herself as an HIV test counselor, reassured, "Your doctor has said everything I would've. But I'll reiterate: It's likely a false positive, and a blood test will confirm. Even if it's not, HIV is not AIDS, and the vast majority of people living in the Western world with insurance will never progress to AIDS. It is a manageable, chronic condition."

In fact, research has shown that for many people with HIV, life expectancies are estimated to be close to those of the general population thanks to the current recommended protocol of combination antiretroviral drugs.

Luckily, the test was a false positive, after all. OP shared her follow-up test results—negative, as she suspected—but here's hoping that by sharing her experience, she served to educate more expectant parents about HIV and the possibility of false positives when you're expecting.

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