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More than 30 percent of births in the United States are now done by cesarean section. Getty Images
  • A new study concluded that C-sections can increase the risk of autism and ADHD for children.
  • Experts say they aren’t sure why there appears to be a link between this type of birth and the disorders.
  • Experts say cesarean sections should still be done when they’re medically necessary.

A new research analysis finds that babies born via C-section are at higher risk of autism spectrum disorders and attention-deficit hyperactivity disorder (ADHD) than those born vaginally.

It’s not the first time that researchers have found an association between autism and cesarean deliveries.

But while the link between the two seems strong, experts still struggle to explain why.

A team of Swedish and Spanish researchers led by Tianyang Zhang of the Karolinska Institutet in Stockholm reviewed 61 past studies on birth modality and connections with autism and ADHD.

The researchers concluded that children born by C-section had a 33 percent higher risk of autism and a 17 percent higher risk of developing ADHD.

C-section deliveries were also associated, although less strongly, with a higher risk of other neurodevelopmental and psychiatric disorders, including learning disabilities, tic disorders, obsessive-compulsive disorder, and eating disorders, according to the study published in JAMA Network.

Notably, the researchers were able to break out emergency from nonemergency C-sections in their review.

They found that “the odds of [autism spectrum disorder] and ADHD in offspring born via elective and emergency cesarean delivery were nearly identical compared with unassisted vaginal delivery.”

Zhang told Healthline that while C-sections are linked to several negative health outcomes in children, such as obesity, asthma, allergies, and type 1 diabetes, the association with neurodevelopmental and psychiatric disorders has been less studied.

Past research has found between a 30 and 80 percent increased risk of autism among C-section babies, Zhang noted.

Given that, the findings by her team were not unexpected.

“When you first see all of the studies and countries involved in this analysis associating deliveries to have a statistical connection between C-section babies and autism and ADHD, it may sound shocking,” Sherry Ross, MD, an OB-GYN and women’s health expert at Providence Saint John’s Health Center in California, told Healthline.

“But when you really look at this statistical significance in this article to those disorders, you can definitely take a sigh of relief. On paper it may seem significant, but in real-time, real-life, it’s not,” she said. “No one really knows the exact cause of autism and ADHD, since we know there are many variables to consider.”

Whether there’s something about the C-section procedure itself that raises the risk of autism and ADHD remains a topic of debate.

“Birth is complicated. There are numerous factors that can lead to different outcomes,” said Zhang. “For example, the emergency C-section we talked about in the paper usually occurs when something goes wrong during a delivery that a surgical intervention becomes necessary. It is not impossible that a child experiences injuries or asphyxia in a traumatic delivery which later result in neurological or neurodevelopmental disorders.”

“Also, C-section is often recommended by obstetricians if the mother has diseases such as diabetes and hypertension,” she added. “Some of the diseases might already have an effect on a child’s brain development when he or she is still in the womb.”

On the other hand, “Other factors related to the C-sections themselves may contribute further to the risk,” Zhang said. “For example, during a natural vaginal birth, specific bacteria from the mother’s gut are passed on to the baby and stimulate the baby’s immune responses. This transmission is altered in children born by C-section.”

“We speculate that it is a combination of these and other factors (e.g. genetic predisposition to neuropsychiatric disorders) that result in increased risks in the offspring,” she said.

The findings shouldn’t be viewed as a warning to mothers against having C-sections, Zhang stressed.

“It would be wrong to demonize C-sections,” she said. “C-sections should continue to be used when medically necessary.”

“This article may discourage couples from having a planned or elective C-section, but it won’t change the overall staggering statistic of how the C-section rate has increased through the years,” said Ross. “There is much work to be done to lower the overall C-section rate of 32 percent in the United States.”

Researchers said further study is needed to determine what’s behind the apparent relationship between C-section and autism and ADHD, including whether the findings vary based on the medical reasons cited for performing a C-section.

“More research is needed to really show causation that C-sections increase the risk of autism and ADHD,” said Ross. “Those wanting to have an elective C-section may take a pause to reconsider knowing this article has some statistical significance, but that may even be a rush to judgement.”