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Being born by Caesarian section may affect your intelligence

Researchers at the University of Bergen looked if there is a connection between the mode of delivery and the genetics of children’s intelligence.

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The number of children delivered by Caesarian section is increasing globally. Still, little is known about the long-term consequences of it. Dinka Smajlagic at Center for Neuropsychiatric Disorders wanted to see if and how mode of delivery may affect the genetics of intelligence in children. She and her fellow researchers analyzed the genome of 2,421 children, looking for possible interplay between genetic factors and mode of delivery on the development of intelligence in children.

"We did not detect any strong genome-wide significant genes", Smajlagic says, "but several potentially relevant loci showed moderating effects on the childhood intelligence, depending on the mode of delivery", the researcher continues.

More specifically – the strongest interaction they observed is between the mode of delivery and genetic variation in the GRIN2A gene that encodes a subunit of a glutamate receptor.

Glutamate is a neurotransmitter linked to a number of neurodevelopmental disorders wich affected intelligence. Thus, genetic variation within GRIN2A gene can influence our intellectual abilities, but that influence may depend on the environment in which the gene is expressed. One of such environmental changes can be the mode of delivery.

Indeed, the study by Smajlagic and colleagues observed that, compared to children born vaginally, children born by Cesarean section show lower intelligence quotient (IQ) score if they possess certain genetic variation within GRIN2A gene.

"Microbes in the gut may alter brain physi­ology and behaviour"

One of the differences between a vaginal delivery and a delivery by Caesarian section is the lack of child’s exposure to maternal gut flora in the latter. This may affect the health of children born by Cesarian section, according to the researchers:

"The method of delivery has been shown also to affect gut colonization and, thus, immunological development of a child. The microbiome content, in turn, may affect your behavior and brain function" .

"More research is needed"

Participants come from the Avon Longitudinal Study of Parents and Childrens (ALSPAC), birth cohort study that recruited more than 14,000 pregnant women from Avon County in Bristol, UK, in the period from April 1991- 1993. The intelligence was measured using Wechsler Intelligence Scale for children, when the children were 8.5 years old.

The researchers excluded other perinatal factors that could confound the effect of mode of delivery on intelligence. The initial model was adjusted for Apgar score at one minute and gestational age.

The researchers are aware that this study has its limitations and Smajlagic underlines that their findings are preliminary only and should be interpreted with caution: "It’s a relatively  underpowered study, suggesting that individual common genetic variants may have gene x environment effects on intelligence. Indeed, it shows that very large studies are needed to conclusively detect variants influencing intelligence in children born by Caesarean section or vaginally."

Read the fullarticle here: https://onlinelibrary.wiley.com/doi/full/10.1002/brb3.1144