Last reviewed: May 12, 2026 Last updated: May 12, 2026

Written by: Jay Hastings , CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance. His work has included scaling healthcare startups, leading CLIA lab integrations, and helping expand consumer access to precision health tools.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

FADS1 and Omega-3s During Pregnancy and Breastfeeding

Pregnancy and breastfeeding are times when your nutrition has a direct effect on fetal and infant brain and eye development. The FADS1 gene helps produce an enzyme that converts plant-based omega-3 fats into the long-chain omega-3s DHA and EPA. These long-chain omega-3s are especially important for the developing brain and retina. Some people have genetic variants that reduce FADS1 enzyme activity, which can make it harder to get enough DHA and EPA from plant sources alone. Knowing your FADS1 genotype can help you plan dietary, supplement, and testing strategies to support a healthy pregnancy and lactation period.

Why DHA and EPA Matter

  • DHA supports fetal brain structure and function and contributes to visual development.
  • EPA plays roles in inflammation regulation and may support maternal mood and cardiovascular health.
  • During pregnancy and breastfeeding, maternal supply of DHA and EPA is the main source for the baby.
  • If conversion from plant omega-3 precursors is impaired, dietary or supplemental preformed DHA and EPA become more important.

Practical Guidance

  • Prioritize direct sources of DHA and EPA if your conversion is reduced: low-mercury fatty fish and algae-based omega-3 supplements are reliable options.
  • Aim for about 600 mg combined DHA and EPA daily during pregnancy and lactation unless your healthcare provider advises differently.
  • If you prefer plant-based diets, choose algae-based DHA supplements to ensure preformed DHA without fish.
  • Continue to include plant sources of ALA, such as flaxseed, chia seeds, walnuts, and canola oil, but do not rely on them alone if conversion may be limited.
  • Limit high-mercury fish (shark, swordfish, king mackerel, tilefish) and focus on low-mercury choices like salmon, sardines, trout, herring, and anchovies.

Diet, Supplements, Lifestyle, and Testing Recommendations

  • Diet: 2 to 3 servings per week of low-mercury, oily fish (salmon, sardines, trout). Include ALA-rich plant foods daily for overall omega-3 intake.
  • Supplements: Consider algae-based or fish oil supplements providing at least 600 mg combined DHA and EPA per day during pregnancy and breastfeeding. If using prenatal supplements that include DHA, check the dose and supplement additional DHA if needed.
  • Lifestyle: Maintain a balanced intake of omega-6 fats to avoid excessive imbalance; avoid smoking and excessive alcohol; manage stress and ensure adequate sleep to support maternal and infant health.
  • Blood tests: Discuss measuring plasma or red blood cell DHA/EPA levels with your healthcare provider if you are concerned about adequacy or have dietary restrictions.
  • Other considerations: If you have known absorption issues, take supplements with a meal containing fat to improve absorption. If you follow a strict vegan diet, algae-based DHA provides a direct, plant-friendly source.
2 effect alleles (TT) — Reduced FADS1 activity

If you have the TT genotype for rs174546, you carry two copies of the effect allele. This genotype is associated with significantly reduced FADS1 enzyme activity, which means your body is much less efficient at converting plant-based omega-3s into the long-chain forms DHA and EPA.

Implications during pregnancy and breastfeeding

  • Greater risk of low DHA and EPA if relying only on ALA-rich plant sources.
  • Because DHA is important for fetal brain and eye development, prioritizing preformed DHA and EPA is important throughout pregnancy and lactation.

Recommended actions

  • Consume 2 to 3 servings per week of low-mercury fatty fish (salmon, sardines, trout), or
  • Take an algae-based or fish oil supplement providing at least 600 mg combined DHA and EPA daily during pregnancy and breastfeeding. If your prenatal contains less DHA, consider an additional supplement to reach the target dose.
  • Include plant omega-3 sources (flax, chia, walnuts) as complementary but not sole sources.
  • Discuss testing of red blood cell or plasma DHA/EPA levels with your healthcare provider to confirm adequacy.
1 effect allele (CT) — Reduced FADS1 activity

If you have the CT genotype for rs174546, you carry one copy of the effect allele. This genotype is associated with reduced FADS1 enzyme activity, so your conversion of plant-based ALA into DHA and EPA is less efficient than average.

Implications during pregnancy and breastfeeding

  • You may be more likely to have lower DHA and EPA if you rely only on plant sources when needs are higher during pregnancy and lactation.

Recommended actions

  • Prefer direct sources of DHA and EPA: 2 to 3 servings weekly of low-mercury fatty fish, or
  • Consider an algae-based or fish oil supplement providing at least 600 mg combined DHA and EPA daily while pregnant and breastfeeding.
  • Continue plant-based ALA sources as part of an overall healthy diet.
  • Ask your healthcare provider about testing DHA/EPA levels if you have dietary limitations or want to confirm status.
0 effect alleles (CC) — Typical FADS1 activity

If you have the CC genotype for rs174546, you carry two copies of the non-effect allele. This genotype is associated with typical FADS1 enzyme activity, meaning your body converts plant-derived ALA to DHA and EPA efficiently.

Implications during pregnancy and breastfeeding

  • You can make effective use of both plant-based ALA and preformed DHA/EPA from food or supplements.
  • Standard omega-3 recommendations for pregnancy and lactation typically apply.

Recommended actions

  • Follow general guidance: aim for 2 to 3 servings weekly of low-mercury oily fish, or use supplements if needed to achieve recommended DHA/EPA intakes.
  • Include plant ALA sources daily for overall omega-3 balance and variety.
  • If you are vegan or avoid fish, consider algae-based DHA supplements to ensure adequate preformed DHA.
  • Speak with your healthcare provider about testing only if you have special dietary concerns or symptoms suggesting deficiency.

When to Talk with Your Healthcare Provider

  • Before starting any new supplement during pregnancy and breastfeeding.
  • If you have dietary restrictions such as vegetarian or vegan diets that limit direct DHA/EPA intake.
  • If you have known malabsorption conditions or chronic illnesses that might affect nutrient status.
  • If you would like laboratory testing to confirm DHA/EPA levels or to tailor dosing.

PlexusDx provides educational genetic information to help you understand how your genes may influence nutrient needs and health. This information is not medical advice. Always consult your healthcare provider before making changes to your diet, supplements, or medical care. Your healthcare provider can integrate your genetic information with your medical history, current health status, and lab results to develop a personalized plan.

If this genetic variant is present in your PlexusDx results, the following tests and reports are commonly used to explore it further:

🧬 Genetic Tests:

🧪 Blood Tests:

📄 Genetic Report:

Frequently Asked Questions About Pregnancy and FADS1 rs174546

How does an FADS1 rs174546 effect allele change omega-3 needs during pregnancy and breastfeeding?

FADS1 helps convert plant omega-3 (ALA) into long-chain omega-3s DHA and EPA. If your FADS1 rs174546 result includes effect alleles (CT or TT), your conversion efficiency is reduced, which can make it harder to meet DHA and EPA needs from plant sources alone during pregnancy and lactation. That often means prioritizing preformed DHA/EPA from food or supplements to better support fetal brain and eye development and maternal health.

What is the best way to get enough DHA and EPA if FADS1 conversion is reduced?

If you have reduced FADS1 activity, focus on direct sources of DHA and EPA. Practical options include low-mercury oily fish (such as salmon, sardines, trout, herring, and anchovies) or algae-based omega-3 supplements (or fish oil) that provide at least 600 mg combined DHA and EPA daily during pregnancy and breastfeeding. Plant ALA sources (flax, chia, walnuts, and canola oil) can still be included daily, but they should not be the only omega-3 source when conversion may be limited.

Should I ask for blood tests to confirm DHA/EPA levels during pregnancy or breastfeeding?

It may be reasonable to discuss testing with your healthcare provider if you have dietary restrictions (e.g., vegetarian/vegan), concern about adequacy, known absorption issues, or other factors that could affect nutrient status. Blood tests such as plasma or red blood cell DHA/EPA levels can help confirm whether you’re meeting DHA/EPA targets. This can guide whether you should adjust food choices and/or supplement dosing, including verifying prenatal DHA amounts and reaching the commonly suggested 600 mg combined DHA/EPA goal unless your provider advises otherwise.

What tests can help me learn more about Pregnancy and FADS1 rs174546?

The Hormone, Thyroid, and Reproductive Health Genetic Test delivers over 85 personalized genetic insights through a comprehensive Hormone & Fertility Genetic Report, explaining inherited tendencies related to hormonal balance, reproductive function, and endocrine signaling. The Womens Hormone and Fertility Health Genetic Report translates your results into personalized, actionable guidance. Your healthcare provider can also recommend targeted blood tests based on your specific pathway results and health history to complement your genetic insights with current biomarker data.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance. References are included at the end of the article when scientific, medical, or health-related claims are discussed.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.