Children who are born by cesarean section are 21% more likely to be diagnosed with an autism spectrum disorder. However, after analyzing those results against sibling pairs, Irish researchers have determined that the association does not mean that c-sections cause autism. Rather, they argue in a new study that the increased risk is more likely due to unknown genetic or environmental factors that could influence the risk of both having a c-section and autism.
Ali S. Khashan, PhD, of the of the Irish Centre for Fetal and Neonatal Translational Research (INFANT), Cork, Ireland, and colleagues examined the association between birth delivery type using registry data from Sweden for live births from 1982 until 2010. This included 2.7 million children. Of that number, 87.4% were delivered by vaginal delivery, while 12.6% were delivered via c-section. A total of 28,290 children (1%) were later diagnosed with autism.
Analyzing these results, the researchers determined there was a 21% higher risk of autism associated with c-sections. However, the authors also conducted a control analysis study involving 13,411 sibling pairs in which one sibling had autism but the other didn’t. Also, in 2,555 pairs, delivery method was discordant with one sibling being born vaginally.
However, in the sibling control study, there was no association between delivery mode and autism, the researchers reported in JAMA Psychiatry.
“Although the traditional cohort analysis revealed birth by [c-section] to be associated with [autism], it is not necessarily a cause because the association could be due to residual confounding,” the authors concluded. “Therefore, because the association between birth by [c-section] and [autism] did not persist in the sibling control analysis, we can conclude that there is no causal association.
“It is more likely that birth by [c-section] is related to some unknown genetic or environmental factor that leads to increased risk of both [c-section] and [autism].”
Khashan AS, et al. Association Between Obstetric Mode of Delivery and Autism Spectrum Disorder: A Population-Based Sibling Design Study. JAMA Psychiatry. 2015; doi:10.1001/jamapsychiatry.2015.0846.