New research suggests that taking antibiotics during pregnancy may be associated with a small increase in the likelihood of a child being diagnosed with attention-deficit/hyperactivity disorder (ADHD). The connection appears to be stronger when antibiotics are used in the second or third trimesters, according to a study recently published in the Journal of Affective Disorders.
ADHD is a neurodevelopmental disorder characterized by hyperactivity, impulsiveness, and difficulty maintaining focus. While genetics play a major role, scientists increasingly recognize that environmental factors before birth may influence the condition.
Antibiotics are among the most commonly prescribed medications for pregnant women, essential for treating bacterial infections that could harm both mother and fetus. However, they can also disrupt beneficial gut bacteria, which are thought to play a role in brain development through what researchers call the gut-brain axis.
Mothers pass some of their gut bacteria to their children, and the prenatal environment can influence early development. Scientists have hypothesized that repeated antibiotic exposure may affect a child’s neurodevelopment, although previous studies have reported mixed results.
To clarify the potential link, a research team led by Jiali Fan from West China Second University Hospital at Sichuan University conducted a meta-analysis of nine high-quality observational studies, including more than 6.1 million mother-child pairs from North America, Europe, and Asia. The studies were evaluated using the Newcastle-Ottawa Scale, a measure of research quality, and were found to be generally moderate to high.
The analysis found that children exposed to antibiotics in the womb had a 15% higher relative risk of developing ADHD. When looking at odds ratios, this risk rose to 28%. Timing also mattered: no significant link was observed for antibiotics taken in the first trimester, but mid- and late-pregnancy exposure showed a modest association.
Frequency of antibiotic use was another key factor. A single course of antibiotics did not increase risk, but repeated courses—two or more—were linked to a higher likelihood of ADHD, suggesting a potential cumulative effect. Sensitivity analyses confirmed that these findings were consistent across different populations.
The researchers caution that this study does not prove causation. Underlying infections themselves, which trigger inflammation and fever, could also influence fetal brain development. Moreover, the analysis could not account for specific antibiotic types or exact dosages, and biological mechanisms remain theoretical, though animal studies support a link between gut microbiota changes and behavior.
The study’s authors recommend careful antibiotic use during pregnancy and call for future research using prospective designs, detailed medication tracking, and sibling comparisons to separate genetic and environmental factors. They emphasize that antibiotics remain critical for treating serious infections and should not be avoided when medically necessary.
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