Expectant moms may have one more reason to get a flu shot.
In research published in the journal Pediatrics, scientists studied the rates of developmental disorders like autism among nearly 97,000 children born in Denmark between 1997 and 2003. The children’s mothers answered questions about infections they might have had during pregnancy — colds, sinus infections and urinary tract infections, among others. They also reported whether they’d suffered from the flu or had fevers that lasted more than seven days before they gave birth.
When the researchers compared the mothers’ answers to the registry of developmental disorders, they found that moms who fought the flu while expecting had children with double the risk of being diagnosed with autism before their third birthday. Mothers who endured flu-based fevers for seven days or more had triple the likelihood of having kids with autism, and those mothers also had a 60% greater chance of having a child diagnosed with developmental difficulties falling into the more expansive category of autism spectrum disorders (ASD). In addition, moms who used antibiotics while pregnant had children with a small increased risk of autism. Infections and antibiotic use can also contribute to low birth weight babies, another risk factor for developmental abnormalities; in a 2011 study, researchers concluded that premature babies who weigh less than 4.5 pounds are five times as likely to be diagnosed with an ASD.
Influenza seemed to be the only infection linked to a higher risk of autism among these mothers’ children; other common infections such as colds and sinus infections during pregnancy did not seem to increase autism among their offspring. While it’s not clear why influenza is so potentially harmful to early development, experts suspect that the fevers associated with flu might be largely responsible, since previous studies show that periods of high fever during pregnancy are associated with birth defects. So bringing down rising body temperatures while expecting is a must, they say, to avoid potentially detrimental effects on a still-growing baby.
Still, as worrisome as the results sound — after all, avoiding the flu isn’t entirely in a mom-to-be’s control — Coleen Boyle, director of the National Center on Birth Defects and Developmental Disabilities (one of whose members contributed to the study) says that the research is “exploratory.”
Adds Dr. Marshalyn Yeargin-Allsopp, chief of the center’s developmental disabilities branch: “It’s important to note that most women experiencing flu, fever or taking antibiotics during pregnancy did not have children with autism spectrum disorders.”
The results however, emphasize the importance of protecting against influenza, particularly for pregnant women, and the researchers urge expectant moms to get vaccinated to protect both themselves and their babies. Throughout gestation and even after birth, for the first six months of life, babies depend on mom for any immunity against bacteria and viruses like influenza. So a flu shot can give an infant a head start in fending off infections from a virus that’s hard to avoid. “It’s flu season and pregnant women should get vaccinated immediately,” says Boyle. Good advice, it seems, for many reasons.