Children whose mothers were given an epidural during labor may face a slightly heightened risk of autism, a large, new study suggests.
Researchers found that the rate of autism was a little higher among those kids, versus their peers whose mothers did not get epidural pain relief during childbirth: 1.9% versus 1.3%.
The reasons for the difference are not yet known. And experts stressed that the findings do not prove epidurals directly raise the odds of a future autism spectrum disorder, or ASD, diagnosis.
"I don't think people should be panicked," said senior researcher Anny Xiang, of Kaiser Permanente Southern California's Department of Research and Evaluation.
For one, she said, the rates of ASD were low in both study groups.
Instead, the findings point to a need for more research to better understand what is going on, Xiang said.
Other experts agreed. Autism is a complex brain-based disorder, and it's thought that many factors -- before, during and after birth -- may influence the risk, said Dr. Rahul Gupta, chief medical and health officer for the March of Dimes.
"It's quite unlikely that just the drugs used in epidural would cause ASD," he said.
Gupta pointed to a bigger-picture question: Women who did or did not have epidurals during delivery may have differed from each other in various ways that the study could not take into account: They may have had different exposures to infections, environmental toxins or medications during pregnancy, for example.
Gupta noted that a large U.S. government study, called SEED, is digging into potential risk factors for autism. It recently found an elevated risk among kids whose mothers were prescribed opioids painkillers shortly before they became pregnant.
When it comes to medications in general, Gupta said, researchers need to learn more about the possible effects during pregnancy.
Autism is a brain disorder that affects social skills, communication and behavior control. It affects about 1 in 54 children in the United States, according to the U.S. Centers for Disease Control and Prevention.
The disorder varies widely from one person to the next: Some children have milder problems with socializing and communicating, while others are profoundly affected -- speaking little, if at all, and getting wrapped up in repetitive, obsessive behaviors.
Genes are thought to account for much of the risk of autism, but experts have long believed that environmental factors also play a role.
Past studies have looked at mode of delivery: Some have found that children born by cesarean section or labor induction have a higher risk of autism.
This latest study, published Oct. 12 in JAMA Pediatrics, is the first to look at epidural use and autism risk.
Xiang's team scoured electronic medical records for nearly 148,000 children born at Southern California hospitals between 2008 and 2015. All were delivered vaginally, and about three-quarters were exposed to epidural analgesia.
Children in that exposed group had a somewhat higher rate of ASD diagnosis. The researchers used the medical records to try to account for other factors -- including the mother's age and education level, and health issues such as diabetes, obesity and smoking.
Even then, children exposed to epidural analgesia remained at 37% greater risk of ASD, compared to unexposed kids.
Xiang's team also looked at one possible explanation: Epidurals can cause a fever and, in theory, that might affect newborns. But there was no clear link between moms' fevers during labor and the risk of autism.
Several medical groups responded to the study, saying it "does not provide credible scientific evidence that labor epidurals for pain relief cause autism."
The groups, including the American Society of Anesthesiologists and the American College of Obstetricians and Gynecologists, said women should not be scared away from opting for an epidural.
"Very low levels of these [epidural] drugs are transferred to the infant, and there is no evidence that these very low levels of drug exposure cause any harm to an infant's brain," the groups said.
Thomas Frazier, chief science officer for the advocacy group Autism Speaks, called the study "high-quality," and said it will hopefully spur more research.
Frazier agreed there may be other explanations for the connection between epidural use and higher ASD risk -- such as infections or other prenatal factors.
Autism Speaks has more on ASD.
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