Reality check: Does herpes during pregnancy double autism risk for your baby?
New research is warning that pregnant women dealing with a herpes flare-up in early pregnancy may be doubling the odds of autism in their unborn baby later on in life. But are other experts agreeing with the findings?
American scientists out of Columbia University’s Mailman School of Public Health say they’re the first to find a link between autism risk in baby and herpes simplex virus-2 (HSV-2) in expectant mom.
“We believe the mother’s immune system response to HSV-2 could be disrupting fetal central nervous system development, raising risk for autism,” the study’s lead author, Milada Mahic, said in a university statement.
It’s not that the risk is due to direct infection of the fetus, the study’s authors explain. It’s the inflammation from herpes and its proximity to the womb that may be tampering with the brain development of the growing babies.
“The cause or causes of most cases of autism are unknown. But evidence suggests a role for both genetic and environmental factors. Our work suggests that inflammation and immune activation may contribute to risk. Herpes could be one of any number of infectious agents involved,” Lipkin said.
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About one in five women in North America carry HSV-2 or genital herpes. It’s spread through sex, is highly contagious and comes with a lifelong infection. After an initial outbreak of herpes, the virus is typically dormant, living in nerve cells but inactive unless it flares ups.
One in 68 children fall under the autism spectrum disorder, according to the U.S. Centers for Disease Control and Prevention. The U.S. federal agency says that’s a 30 per cent jump from its last estimate of one in 88 children – the latest calculations mean autism is more than twice as common as officials said it was years ago.
It’s hard to decipher why cases are on the rise but experts say that it could be because of a raised awareness and doctors who can identify cases better now, especially in children with mild problems.
For their study, the Columbia researchers looked at blood samples from 412 mothers of kids diagnosed on the autism spectrum disorder along with 463 mothers of kids without autism.
Blood samples were taken at two time points – at around week 18 of pregnancy and at birth. The scientists were looking for levels of antibodies to a handful of pathogens, from rubella, to herpes.
Turns out, 13 per cent of the moms tested positive for HSV-2 by mid-pregnancy. Of this group, 12 per cent had herpes lesions before pregnancy or during their third trimester – most infections were asymptomatic and dormant.
The link between herpes and autism risk was only seen in boys. But the study ended up with many more baby boys than girls, the researchers concede. Autism is also more common in males, too. The researchers say there isn’t enough evidence to conclude that the potential effect is sex-specific.
They say that, on the whole, further study is needed to determine if herpes infection needs to be screened and suppressed during pregnancy.
Experts in the field aren’t sold on the findings, though.
“Unfortunately, the analysis conducted in this study has significant flaws, and in fact, the data does not support the claims made by the authors,” Matthew Pletcher, vice-president and head of genomic discovery at Autism Speaks, told CNN.
“Pregnant women should not be worried about HSV-2 (genital herpes) as a cause of autism based upon the findings of this single exploratory research study,” Dr. David Winston Kimberlin, a pediatric infectious diseases specialist at the University of Alabama, told the U.S. outlet.
Another source told CNN that the findings are “subject to concern.”
Dr. Peter Hotez, a vaccine scientist and pediatrician at Baylor College of Medicine, told Science Magazine that he’s skeptical, too.
“The changes in the architecture of the neocortex in the brains of kids with autism are so profound that it’s hard to imagine how an inflammatory response, even in utero, is going to cause that [autism risk], he said.
About 16 per cent of women between 14 and 59 have genital herpes, according to Statistics Canada. It’s one of the most common sexually transmitted infections.
Symptoms can vary from no warning signs at all to outbreaks of itchy, painful blisters around the opening of the vagina. Sometimes women encounter flu-like symptoms, such as fever, headache and muscle aches.
The full findings were published in mSphere, a journal of the American Society for Microbiology.
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