Though the first analysis showed an association, adjustment for a wide range of demographic, medical, and birth factors eliminated the link. The authors note that their findings are different from those reported in a study in California published in the same journal last year.
The researchers examined data from all infants born from 2005 to 2016 at a hospital in Manitoba, Canada, to compare use of epidurals during birth with diagnoses of autism before 18 months of age. The researchers excluded women with cesarean deliveries because it was not possible to differentiate between scheduled and unscheduled cesarean deliveries.
The study looked at 123,175 children born to mothers with an average age of 28 years. Of the mothers,, 38.2% used an epidural during their labor. Autism diagnoses occurred among 2.1% of the children exposed to epidurals and 1.7% of those who were not. After the researchers controlled for a range of potential factors, the difference was insignificant.
The findings are important but unsurprising, said Scott M. Myers, MD, a neurodevelopmental pediatrician and associate professor at the Geisinger Commonwealth School of Medicine’s Autism & Developmental Medicine Institute in Scranton, PA. Myers, who was not involved in the study, said it was strengthened by the inclusion of a wide range of variables.
“It confirms the suspicion of many experts who were skeptical of the association reported previously, that the small increase in ASD in offspring of mothers who had epidural labor analgesia was likely attributable to other factors,” Myers said in an interview. “The plausibility of exposure to epidural analgesia in labor having a large effect on ASD risk and accounting for changes in ASD prevalence over time is low.”
Myers said that epidurals can lead to longer labor. If long labor was a significant risk factor for autism, it would be expected that there would be evidence that extended labor led to increased autism risk. “But this has been examined and is not the case,” he said.
Clay Jones, MD, who specializes in neonatal medicine at Newton Wellesley Hospital in Newton, MA, was not involved in the research and offered a similar assessment of the findings.
“Our understanding of autism is that it is more of a genetic condition which interferes with the organization of brain architecture, so the evidence for any environmental cause would need to be robust for it to change medical practice or our recommendations to the general public,” Jones said in an interview. Compared to the previous California study, “this new research is larger and better accounts for confounding variables that might increase the risk of a child eventually being diagnosed with autism,” he said.
The authors of the study also noted the benefits of epidural use during labor.
“It is recognized as the most effective method of providing labor analgesia,” they write.