Emerging research continues to highlight the remarkable role of omega-3 fatty acids in supporting pregnancy outcomes — and now, a compelling new study from Denmark suggests that increasing a pregnant woman’s blood levels of EPA and DHA may significantly reduce her child’s risk of developing asthma.
This finding strengthens the case for routine DHA supplementation during pregnancy, especially for women with low baseline omega-3 levels. In this post, we explore the details of the study, its implications for U.S. mothers, and what it means for prenatal omega-3 strategies.
Why Asthma Prevention Matters
According to the Centers for Disease Control and Prevention (CDC):
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Asthma affects 8.6% of children under 18 (over 6 million kids)
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It’s the leading chronic illness in children
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It’s the top cause of missed school days
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It’s the third leading cause of pediatric hospitalizations
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Asthma care costs the U.S. approximately $56 billion annually
With such a staggering toll, the prospect of reducing asthma risk through simple dietary changes during pregnancy is both exciting and impactful.
The Danish Study: A Gold-Standard Clinical Trial
This was no ordinary research project. The Danish team designed a rigorous, randomized, double-blind, placebo-controlled trial involving 736 healthy pregnant women.
Key Study Details:
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Participants recruited at 22–26 weeks gestation
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At week 24, women received either:
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2400 mg/day of EPA + DHA (from fish oil; 55% EPA, 37% DHA)
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Placebo (olive oil)
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Supplementation continued through one week postpartum
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Blood and breast milk samples were collected
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Pediatricians blinded to group assignments tracked the children for up to five years
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Asthma diagnoses and wheezing symptoms were algorithmically confirmed
What They Found: Omega-3s Help Reduce Asthma Risk
Omega-3 Blood Levels Increased as Expected
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Supplemented moms saw EPA+DHA levels rise from 4.9% to 6.1% (whole blood)
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In contrast, the placebo group dropped to 3.7%
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These changes translate to an Omega-3 Index increase from 6.9% to 8.3% in the treatment group — and a decline to 5.5% in the placebo group
Notably, these women started with higher-than-average omega-3 levels due to a fish-rich Danish diet (~321 mg/day EPA+DHA). This is far higher than U.S. women, who average just ~90 mg/day.
Most Impactful for Women With Low Omega-3 Status
Across the entire study group (n=695 children):
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Asthma incidence dropped from 24% (placebo) to 17% (omega-3 group)
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That’s a 31% relative risk reduction
But here’s where it gets even more impressive:
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In mothers with low baseline omega-3 levels (<4.3% EPA+DHA)
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Their children’s asthma risk was reduced by a staggering 54% with supplementation
This is especially relevant for the U.S., where average omega-3 levels in women of childbearing age hover around 4% Omega-3 Index — meaning a large portion could benefit significantly from supplementation.
Breast Milk Omega-3s: Less Predictive for Asthma
The study also measured EPA+DHA in breast milk at one month postpartum. Interestingly, these levels did not strongly correlate with asthma outcomes.
Possible reasons include:
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Supplementation was stopped at 1 week postpartum, yet milk was tested at 1 month — meaning omega-3 levels may have already dropped.
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Breast milk fatty acid levels adjust quickly (within 2 weeks), while red blood cell levels change over 3–4 months.
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The study supports the idea that prenatal omega-3 status may be more influential on long-term outcomes than short-term postnatal levels.
The Case for Omega-3 Testing During Pregnancy
One of the most exciting takeaways is the potential for targeted supplementation based on omega-3 testing. The lead researcher, Dr. Hans Bisgaard, emphasized in an interview:
“Pending further study, the best way to apply the findings would probably be to test women for fatty acid levels in their blood... to determine who might benefit from fish oil.”
Tools like the Omega-3 Index test can help identify low-risk women and tailor DHA supplementation strategies accordingly.
Omega-3s and Pregnancy: Expert Recommendations
The benefits of omega-3s during pregnancy go beyond asthma prevention. DHA in particular has been linked to:
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Support for a healthy immune response in both mother and child
Because of these wide-reaching benefits, organizations like the American Academy of Pediatrics and Global Organization for EPA and DHA Omega-3s (GOED) encourage daily DHA intake of at least 200–300 mg during pregnancy.
