Caesarian section (C-section) deliveries may contribute to the development of autism among babies, finds a new study published in the Journal of Child Psychology and Psychiatry.

Study researchers from the University of College Cork (UCC) have discovered a link between C-section delivery with “modest increased odds” of Autism Spectrum Disorder (ASD) and perhaps Attention Deficit and Hyperactivity Disorder (ADHD) as well as compared to natural or vaginal delivery.

“Although the effect may be due to residual confounding, the current and accelerating rate of CS implies that even a small increase in the odds of disorders, such as ASD or ADHD, may have a large impact on the society as a whole,” researchers say.

It remains unclear, however, why the said medical procedure appears to intensify the chances of developing the condition, the study says.

The UCC researchers found that babies who were born through C-section may have a higher chance of developing ASD by 23 percent.

Further according to the study, C-section deliveries are prevalent approximately worldwide by 15 percent and in developing countries by 20 percent—and are still growing yearly. The high prevalence is attributed to economic, societal, and clinical issues.

The researchers likewise discovered that approximately 0.62 percent worldwide was diagnosed with ASD, while an estimate of 5.3 percent was found to have ADHD. The prevalence of ASD increased by 20-fold since the 80s.

“Given the growing prevalence of birth by Caesarean section (CS) worldwide, it is important to understand any long-term effects CS delivery may have on a child's development,” reads the study.

ADHD and ASD are said to be highly heritable, the study also suggests. However, new evidence suggests that environmental factors also play a role in the development of the said conditions.

Various studies in the past and at present have also linked birth deliveries by C-section with several other health conditions such as diabetes, allergic rhinitis, offspring asthma, bipolar disorder, gastrointestinal disease, and neurological development issues.

The researchers clarify, however, that more studies are needed to completely confirm such findings and explore the possible risks, and that the risk remains small.

“Parents should be reassured that the overall risk of a child developing ASD (Autism Spectrum Disorder) is very small and that Caesarean section is largely a very safe procedure and when medically indicated, it can be lifesaving,” says obstetrician and professor Louise Kenny, who is also one of the authors of the study.

The UCC study, titled Research Review: Birth by caesarean section and development of autism spectrum disorder and attention-deficit/hyperactivity disorder: a systematic review and meta-analysis, was first published online on Oct. 27.