A decade-long study from Danish researchers finds that a specific fatty acid in a pregnant woman’s blood is strongly linked to her child’s asthma risk — and may determine whether omega-3 supplements during pregnancy actually help.
A fatty acid molecule called 12-HETE could be a key missing piece in understanding why some children develop asthma and others don’t — and new research suggests that its presence, or absence, in a pregnant woman’s blood may shape her child’s respiratory health for years to come.
Researchers from the University of Copenhagen and Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) at the Danish Pediatric Asthma Center at Herlev and Gentofte Hospital tracked hundreds of mothers and their children over 10 years, measuring fatty acid levels in maternal blood and monitoring children for asthma, respiratory infections and airway bacterial composition. Their findings, published in Cell Reports Medicine, show that children born to mothers with undetectable levels of 12-HETE during pregnancy were 62% more likely to develop asthma during their first decade of life.
“For the first time, we show that a specific fatty acid molecule in pregnant women is linked to the child’s risk of developing asthmatic bronchitis: If the mothers do not have a measurable amount of this molecule in their blood during pregnancy, there is a higher occurrence of childhood asthma in the child’s first year of life,” corresponding author Bo Chawes, a clinical professor and asthma researcher from the University of Copenhagen’s Department of Clinical Medicine and COPSAC, said in a news release.
Why It Matters
Childhood asthma, often called asthmatic bronchitis, is one of the most common chronic illnesses in children worldwide. It causes recurring episodes of wheezing, coughing and shortness of breath, and its origins are still not fully understood. Scientists increasingly believe that conditions in the womb — not just genes or early-life environment — play an outsized role in determining whether a child will develop the disease. This study adds a specific, measurable biological signal to that picture for the first time.
The researchers collected blood samples from pregnant women at week 24 of pregnancy and then followed the health of the mothers and children closely, analyzing airway bacteria and diagnosing asthma over the ensuing decade. The study is based on data from two large mother-child cohorts: the Danish COPSAC2010 cohort, which included 738 mothers and 700 children, and the American VDAART cohort, which included 881 women and 810 children. Findings from the Danish group were validated using data from the American cohort.
“It is in itself a major strength that we follow more than 700 women and their children intensively with biological samples and symptom monitoring, all the way until the children are ten years old. We do not demonstrate a causal relationship, but the study is strengthened by the fact that we can replicate our findings in an American cohort with a fairly identical design,” Chawes added.
A Ripple Effect Starting Before Birth
The research also uncovered early biological differences in children born to mothers without detectable 12-HETE. By the time those infants were just one month old, their airways already showed altered bacterial communities and different immune responses compared with children whose mothers had measurable levels of the fatty acid.
“As early as when the child is one month old, we can see a completely different bacterial composition and immune response in their airways if we cannot measure 12‑HETE in the mothers’ blood. And we know that these factors are crucial for the risk of developing asthma,” added Chawes.
The researchers believe 12-HETE plays a central role in priming the infant immune system — a process that begins before birth.
“It appears that 12‑HETE is crucial in the early maturation of the child’s immune system. If the child very early – already in the womb – has too low levels of these fatty acids, this likely leads to an immune system that does not function well enough and consequently results in an altered lung microbiome. And that can increase susceptibility to respiratory infections and the development of asthma,” Chawes added.
Rethinking Omega-3 Supplements During Pregnancy
One of the study’s most practically significant findings concerns omega-3 fatty acids, commonly found in fish oil and widely discussed as a supplement during pregnancy. Prior research has shown that omega-3 supplementation can, in some cases, reduce the likelihood of children developing asthma — but results have been inconsistent across studies. This new research offers a potential explanation for that inconsistency.
In a randomized trial embedded within the Danish cohort, pregnant women received either omega-3 supplements or a placebo. The researchers then looked at whether the effect of supplementation varied based on the mothers’ 12-HETE levels. The results were striking: among mothers with measurable 12-HETE, omega-3 supplementation was associated with a 58% lower rate of early childhood asthma compared to the placebo group. Among mothers without detectable 12-HETE, supplementation appeared to make no difference at all.
“We show that 12‑HETE is crucial for whether omega‑3 supplementation during pregnancy has a protective effect against childhood asthma. In other words, it is not certain that all pregnant women will benefit from the same supplements, but in the future, we may be able to identify those who will gain the greatest benefit,” Chawes added.
Not Ready for the Clinic — Yet
The researchers are careful to note that the study establishes a statistical association, not a proven cause-and-effect relationship. Before 12-HETE testing could be used to guide clinical decisions — such as advising specific pregnant women to take omega-3 supplements — more work is needed to establish concrete measurement thresholds and to confirm the findings in even larger populations.
Still, the implications for precision medicine in pregnancy care are clear.
“Childhood asthma is extremely common, and therefore it is crucial to find out what drives it and how we can prevent it. With our study, we have shown that 12‑HETE could potentially function as a biomarker and thus represent the first step toward a more personal and precise prevention of childhood asthma,” Chawes said.
For college students studying medicine, public health, biology or health policy, the research is a reminder of how dramatically the field of preventive medicine is shifting — from one-size-fits-all recommendations toward targeted interventions guided by individual biology. A simple blood test during pregnancy could, in the future, help clinicians identify which mothers and children are most at risk and which interventions are most likely to help.
Source: University of Copenhagen