CDC relaxed their guidelines on testing for Zika in pregnant women. But is this a good thing for your health—and the health of your baby?

By Tina Donvito
July 26, 2017
Zika virus testing
Credit: Rostislav_Sedlacek/Shutterstock

The Zika virus and the birth defects it could inflict have struck fear in pregnant women since the disease spread to the Americas two years ago. Although the Centers for Disease Control and Prevention (CDC) had been testing every pregnant woman with possible exposure, the organization relaxed its rules this week, with new guidelines saying women do not need to be tested unless they have ongoing exposure or have symptoms. But does that mean some women without symptoms could slip through the cracks?

Flawed testing

Here's the problem with the testing, as the CDC's report notes: New evidence has shown that it's not always accurate, resulting in a lot of false positives. The test looks for antibodies in the blood that are fighting off the infection, but these antibodies could linger for more than 12 weeks, making it difficult to know whether the actual infection occurred before or during pregnancy. Plus, the CDC says the number of cases has thankfully been declining—but as that happens, the number of false positives in the test goes up.

Although routine testing is no longer recommended, if you live in or have traveled to areas where the virus is present, you should still talk with your doctor about your individual risk and whether you should be screened. The CDC's new guidelines emphasize "shared decision-making" between patients and providers based on "patient preferences and values, clinical judgment, and a balanced assessment of risks and expected outcomes." So if you're concerned about your risk, definitely bring it up.

Even so, testing for the virus is tricky. "While it is encouraging that we have gathered more epidemiologic information that can help us refine recommendations, there are still a lot of unknowns about the virus during pregnancy, including when is the highest risk period for transmission and at what point after exposure a risk subsides," Clara Ward, MD, a maternal-fetal medicine specialist at McGovern Medical School at UTHealth and Children's Memorial Hermann Hospital in Houston, tells "This makes existing counseling challenging in these low-risk exposure situations, especially when testing cannot always exclude Zika virus."

A potential for missed cases?

Does less testing mean more women who are infected with the Zika virus will be missed? "Many women are likely at low risk for contracting Zika virus without ongoing exposure," Dr. Ward says. "It is unlikely that any potential cases missed by minimizing testing in low-risk asymptomatic pregnant women will outweigh the risk of anxiety caused by false positive results in an otherwise low-risk situation."

Will less testing in pregnant women mean that pediatricians will have to be more vigilant in their diagnosis of newborns who may have been affected by the virus? "The new guidelines will not affect pediatricians much," says Trew Stransky, DO, a pediatrician at Rockford Pediatrics in Rockford, Michigan. "Pediatricians will continue to monitor babies after birth for signs of obvious birth defects, such as microcephaly [small head size]. Fortunately, only two to 10 percent of infants born to mothers with Zika will contract the disease."

Avoiding exposure is still the best way to go in preventing the disease. The travel restrictions for women who are pregnant or planning to become pregnant and their partners are still in place. If you live in areas at risk for the virus, the CDC offers mosquito-prevention strategies, since those little suckers spread it. And although many infected people don't have symptoms, if you experience fever, rash, headache, red eyes, or joint or muscle pain, let your doctor know immediately.