Children who were born via cesarean section delivery were 21% more likely to be diagnosed with autism spectrum disorder (ASD) but this link was not found to be causal upon further analysis of sibling pairs, new research has found. Findings from the study are published in JAMA Psychiatry.

Researchers from the Irish Centre for Fetal and Neonatal Translational Research (INFANT) in Cork, Ireland examined the relationship between modes of delivery (specifically birth by cesarean section) on ASD using data from the Swedish registry for live births from 1982–2010. The study included close to 2.7 million children, 80.1% (n=2.1 million) of whom were born by unassisted vaginal delivery, 6.1% (n=164,305) by elective cesarean section delivery, 6.5% (n=175,803) by emergency cesarean section delivery, and 7.3% (n=196,058) by assisted vaginal delivery. One percent (n=28,290) of children were diagnosed with ASD.

A sibling control study included 13,411 sibling pairs where one sibling had ASD while the other did not; and 2,555 siblings pairs had different methods of delivery with one sibling born through unassisted vaginal delivery.

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Though the initial cohort study showed children born by elective cesarean section delivery were 21% more likely to be diagnosed as having ASD, the sibling control analysis showed no association between mode of delivery and ASD.

Since the link between cesarean section delivery and ASD did not persist in the sibling control analysis, researchers concluded that there was no causal association.A cesarean section birth may be related to an unknown genetic or environmental factor that increases the risk of cesarean section and ASD.

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