Researchers from The Chinese University of Hong Kong studied how two biological systems—epigenetics (genetic switches that turn genes on or off) and gut bacteria—interact from birth to age three. They tracked 571 infants' DNA methylation patterns (a type of genetic switch) in umbilical cord blood, collected gut bacteria samples from 969 infants at 2, 6, and 12 months, and assessed their neurodevelopment at age three using behavioral questionnaires.
The study looked for links between these genetic patterns, gut bacteria, and signs of autism spectrum disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) by age three. This research was published in Cell Press Blue.
Babies born by Caesarean show different genetic patterns linked to immunity and brain genes
The researchers found that birth method, pregnancy length, having older siblings, and maternal allergies all influenced a baby's genetic switches at birth. Infants born via Caesarean section showed notably different DNA methylation patterns in genes involved in immune function and brain development. Importantly, parental gut bacteria did not directly influence these birth-related genetic changes—suggesting the baby's own biological programming matters most at this stage.
A 'conversation' between genes and gut bacteria shapes early development
The study revealed something unexpected: while a baby's genetic settings at birth can increase risk for neurodevelopmental differences like ASD and ADHD, certain beneficial bacteria in the gut could actually step in and modify that risk. Different factors shaped the infant microbiome during the first year compared to what influenced genetic patterns at birth. Delivery method, antibiotic exposure, having older siblings, and breastfeeding all played roles in which bacteria colonised a baby's gut. The research suggests these systems are communicating—genes influence which bacteria grow, and specific bacteria may then protect brain development.
Evidence is early; follow-up studies needed
This study is important because it's one of the first to show how epigenetics and microbiome interact during infancy. However, the research only tracked children to age three and comes from one region, so we cannot yet say whether these patterns predict long-term neurodevelopmental outcomes or whether they apply across all populations. The researchers note that while protective bacteria are exciting, we still need more evidence before recommending specific diets or probiotics for infants.
What this finding means for your family
- Breastfeeding, delivery method, and antibiotic use in infancy shape gut bacteria—discuss these with your child's doctor if concerned.
- If your baby was born by Caesarean, mention it to your paediatrician; they can monitor development and discuss gut health.
- Avoid unnecessary antibiotics in early childhood when possible, as they alter beneficial bacteria development.