Regular testing for HIV is part of pregnancy these days, which bumps up the chance you might get a false-positive result. Experts explain why that can happen.

By Maressa Brown
January 17, 2020
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Growing a human for nine months can be stressful for many reasons—one of them being all the testing and blood work that needs to be done 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 was contending with recently, 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 women in the subreddit had gotten false positives as well, so she wanted to share her situation with the community.

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 percent 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 women, 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 and 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 woman’s body will react and result in a false-positive test," says Dr. Gersh. "When the screening test of a pregnant woman returns a positive result, a different type of test, called the Western blot (WB) is run as the confirmatory 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 women get the vaccine, so it may be more prevalent for the women getting tested)
  • Presence of HLA-DR antibodies in women 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 there is a pregnancy-specific factor that 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 women.

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 a major issue for the OP to be aware of. "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, recent research published in the journal AIDS found that the additional life expectancy is nearly 55 years for people on the current recommended protocol of combination antiretroviral drugs.

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

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