Fish oil supplementation during pregnancy may leave measurable effects on a child’s brain metabolism for at least a decade, according to findings from a long-running randomised controlled trial.
Children whose mothers received omega-3-rich fish oil during late pregnancy showed slightly lower cerebral blood flow and oxygen consumption at age 10 than children whose mothers received a placebo. These two measurements normally decline as the brain matures from childhood into adulthood, leading researchers to suggest that prenatal supplementation may influence the timing or pattern of brain metabolic development.
However, the findings should not be interpreted as proof that fish oil makes children more intelligent, improves mental health or produces a healthier brain. The metabolic differences were small, and they were not linked to better cognitive performance or fewer psychiatric symptoms.
The study was published in Translational Psychiatry and used data from the Copenhagen Prospective Studies on Asthma in Childhood 2010 cohort.
The Trial Followed Children for a Decade
The original study included 700 pregnant women from the COPSAC2010 cohort in Denmark. Beginning at the 24th week of pregnancy, participants were randomly assigned to receive either fish oil-derived omega-3 fatty acids or an olive-oil placebo.
The supplementation continued from pregnancy week 24 until one week after delivery. The fish oil group received 2.4 grams of long-chain omega-3 polyunsaturated fatty acids each day, with the formulation containing approximately 55% eicosapentaenoic acid, or EPA, and 37% docosahexaenoic acid, or DHA.
Because the trial was double-blinded and randomised, neither the participants nor the main investigators knew which treatment had been assigned during the intervention. That design provides stronger evidence of a possible causal effect than an observational study in which people independently choose whether to consume fish oil. The original trial is also registered through ClinicalTrials.gov.
Approximately 10 years later, 487 children underwent 3-tesla magnetic resonance imaging. Following processing and quality-control procedures, 460 children had at least one usable brain-metabolism measurement. The fully adjusted analyses included different numbers of children depending on the particular scan and available data.
Two Brain Metabolic Markers Were Lower
Researchers examined three main measurements: cerebral blood flow, the cerebral metabolic rate of oxygen and lactate concentration in a brain region called the precuneus.
Cerebral blood flow describes how much blood passes through brain tissue over a given period. That blood delivers oxygen and nutrients required to support neural activity.
The cerebral metabolic rate of oxygen, commonly abbreviated as CMRO₂, estimates how much oxygen the brain consumes. It provides information about the energy demands of brain tissue rather than simply showing how much blood reaches it.
Children in the fish oil group had an average cerebral blood flow approximately 2.3 millilitres per 100 grams of brain tissue per minute lower than children in the placebo group. Their cerebral oxygen consumption was also approximately 17.38 micromoles per 100 grams per minute lower. Both differences reached statistical significance.
The third marker, lactate concentration in the precuneus, did not differ significantly between the groups. The results therefore involved two of the three metabolic measurements rather than a broad change across every marker examined.
Lower Brain Metabolism Does Not Automatically Mean a Better Brain
The childhood brain consumes unusually large amounts of energy. Processes such as synapse formation, neural pruning and myelination contribute to higher blood flow and oxygen use than are generally observed in adulthood.
Cerebral blood flow and oxygen consumption tend to increase during early childhood, peak at approximately seven years of age and gradually decline through adolescence and adulthood. Children also typically show higher levels of brain lactate production than adults.
To place the results in a developmental context, the researchers compared the children’s data with brain measurements from 248 adults scanned using the same equipment and imaging methods. Increasing age was associated with lower cerebral blood flow, oxygen metabolism and lactate concentration.
This comparison made the fish oil group’s measurements appear slightly more adult-like. The researchers therefore proposed that maternal omega-3 supplementation might influence brain maturation.
That interpretation remains tentative. A lower metabolic rate in one scan does not prove that a child’s brain has matured faster, operates more efficiently or will perform better later in life. Repeated scans throughout childhood would be needed to show whether the children followed genuinely different developmental trajectories.
The Changes Were Not Linked to Intelligence or Mental Health
The children completed cognitive assessments and evaluations covering behavioural and psychiatric symptoms. Researchers examined whether cerebral blood flow, oxygen consumption or lactate levels were associated with cognition or psychopathology.
No statistically significant relationships were detected. The metabolic measurements were not linked to improved cognitive performance, fewer behavioural difficulties or lower levels of symptoms associated with conditions such as attention-deficit/hyperactivity disorder or autism spectrum disorder.
This result does not prove that prenatal fish oil has no influence on neurodevelopment. Some diagnostic groups contained relatively few children, and a study of this size may not detect small or condition-specific effects.
Nevertheless, the absence of a measurable cognitive advantage is central to understanding the findings. The trial identified biological differences on MRI, not demonstrated improvements in intelligence, academic ability or mental health.
Why Omega-3 Fatty Acids Could Influence Brain Development
DHA and EPA are long-chain omega-3 fatty acids commonly obtained from oily fish and fish oil supplements. DHA is highly concentrated in the brain and retina and accumulates rapidly during the third trimester of pregnancy.
These fatty acids contribute to cell-membrane structure and are involved in signalling, inflammation and nervous-system development. The timing of the intervention therefore covered a period when the fetal brain was undergoing substantial growth and DHA accumulation.
Despite the biological importance of omega-3 fatty acids, previous supplementation trials have not produced consistent evidence of improved childhood cognition or visual development. The National Institutes of Health’s omega-3 fact sheet notes that sufficient long-chain omega-3 intake is important during pregnancy, but findings on cognitive benefits from supplements remain mixed.
The new study adds a different kind of evidence. Rather than focusing only on test scores or developmental milestones, it shows that prenatal supplementation may produce subtle changes in brain physiology that remain detectable many years later.
Randomisation Strengthens the Findings
A major strength of the research is its randomised design. Mothers were assigned to supplementation or placebo rather than grouped according to their existing dietary habits.
The researchers also examined EPA and DHA levels measured before the intervention. Those baseline levels were not significantly associated with the children’s later brain measurements, whereas the randomised supplementation was associated with lower cerebral blood flow and oxygen consumption.
This contrast supports the possibility that the intervention itself contributed to the differences. It does not establish that the same result would occur with every dose, supplement formulation or pregnancy population.
Several Limitations Prevent Firm Conclusions
The study involved a single Danish cohort, which may limit how confidently the results can be applied to more diverse populations. Not every original participant completed the 10-year imaging visit, and the fully adjusted sample sizes were smaller than the original group of 700 mother-child pairs.
Brain metabolism was measured at one point in childhood. Without scans from infancy, earlier childhood and adolescence, researchers cannot determine exactly when the differences developed or whether they will continue into adulthood.
Cerebral blood flow and oxygen consumption were assessed globally rather than across every specific brain region. Lactate was measured only in the precuneus, meaning possible changes elsewhere in the brain could have been missed.
The adult comparison was also cross-sectional. It showed that adults generally had lower metabolic measurements than children, but it did not follow the same individuals across the lifespan.
The Study Does Not Support Self-Prescribing High-Dose Fish Oil
The trial used a relatively substantial daily dose of fish oil under research supervision. Its findings do not establish that pregnant women should independently begin taking 2.4 grams of omega-3 fatty acids to alter their child’s brain development.
Current evidence more clearly supports obtaining omega-3 fatty acids through an appropriate diet. The US Food and Drug Administration recommends that pregnant or breastfeeding people consume eight to 12 ounces of lower-mercury seafood each week. Its fish-consumption guidance includes choices such as salmon, sardines, trout and oysters.
Supplement requirements can differ according to diet, health conditions, DHA intake and medication use. Fish oil may also interact with some medicines, including anticoagulants, particularly at higher doses. Supplement decisions during pregnancy should therefore be discussed with a qualified healthcare professional.
A Biological Difference Without a Proven Clinical Benefit
The research provides evidence that prenatal nutrition may shape childhood brain physiology long after pregnancy has ended. Fish oil supplementation from week 24 of pregnancy through one week after birth was associated with lower cerebral blood flow and lower oxygen consumption at age 10.
Those differences resembled the direction normally seen as the brain moves toward adulthood, but the study did not prove faster or healthier maturation. It also found no corresponding improvement in cognition or mental-health outcomes.
The findings are therefore scientifically important without yet being clinically actionable. They show that omega-3 exposure during pregnancy can leave a detectable metabolic signature in the child’s brain, while leaving the meaning of that signature unresolved.
