Pregnancy | FADS2 (rs1535)

FADS2 and Omega-3s in Pregnancy: What Your Genotype Means for Baby and You

Pregnancy is a time when your nutrition directly supports the growth and development of the baby’s brain, eyes, and nervous system. The FADS2 gene helps your body convert plant-based omega-3 fat (ALA) into the active forms EPA and DHA. EPA and DHA are especially important during pregnancy and breastfeeding. Some people have genetic variations that reduce FADS2 activity and make it harder to produce enough EPA and DHA from plant sources alone.

Why EPA and DHA Matter

EPA and DHA are long-chain omega-3 fatty acids needed for fetal brain and eye development and for healthy nervous system function.
DHA accumulates in the developing fetal brain and retina, particularly in the third trimester and during early infancy.
Low maternal EPA and DHA can increase the risk of insufficient fetal stores. Pregnant and lactating people have higher needs than those who are not pregnant.

How Genetics Affects Conversion

The FADS2 enzyme converts alpha-linolenic acid (ALA) from plant foods like flaxseed, chia seeds, and walnuts into EPA and DHA. The rs1535 genetic variant influences how well this enzyme works. Different genotypes correspond to different conversion abilities, which can affect how much direct dietary EPA and DHA you need during pregnancy and breastfeeding.

2 effect alleles (GG) — lowest conversion activity

If your genotype is GG at rs1535, you carry two copies of the effect allele. This genotype is associated with the lowest FADS2 enzyme activity, which means your body has severely reduced ability to convert ALA into EPA and DHA.

Implications during pregnancy and lactation

Higher risk of low maternal EPA and DHA when relying on plant sources alone.
Greater need for direct dietary or supplemental EPA and DHA to support fetal brain and eye development.

Practical recommendations

Consume 2–3 servings per week of low-mercury fatty fish such as salmon, sardines, or trout when possible.
If avoiding fish, take an algae-based omega-3 supplement providing at least 600 mg/day combined EPA and DHA throughout pregnancy and lactation.
Include ALA-rich plant foods (flaxseed, chia, walnuts) for overall diet quality but do not rely on them alone for EPA and DHA.
Discuss omega-3 blood testing and supplement dosing with your healthcare provider to ensure adequate levels.

1 effect allele (AG) — reduced conversion activity

If your genotype is AG at rs1535, you carry one effect allele. This genotype is associated with reduced FADS2 enzyme activity, which lowers your ability to convert ALA into EPA and DHA compared with the AA genotype.

Implications during pregnancy and lactation

You are more likely than someone with AA to have lower EPA and DHA if you rely mainly on plant sources.
Your needs for direct EPA and DHA are higher than if conversion were fully efficient.

Practical recommendations

Aim for 2–3 servings per week of low-mercury fatty fish such as salmon or sardines.
Consider an algae-based omega-3 supplement that provides at least 600 mg/day combined EPA and DHA during pregnancy and breastfeeding.
Keep ALA-rich foods in the diet for variety and overall nutrition, but prioritize direct EPA and DHA sources.
Talk with your clinician about monitoring DHA levels if you have dietary restrictions or are concerned about intake.

0 effect alleles (AA) — typical conversion activity

If your genotype is AA at rs1535, you carry two copies of the non-effect allele. This genotype is associated with typical FADS2 enzyme activity and a higher ability to convert ALA into EPA and DHA than AG or GG genotypes.

Implications during pregnancy and lactation

Your body is likely better at converting plant-based ALA into EPA and DHA, but pregnancy increases overall needs.
Even with normal conversion, obtaining direct dietary EPA and DHA helps meet the higher demands of pregnancy and breastfeeding.

Practical recommendations

Include 2–3 servings per week of low-mercury fatty fish such as salmon, sardines, or trout where possible.
If fish is avoided, consider algae-based omega-3 supplements to ensure adequate DHA and EPA during pregnancy and lactation.
Continue to include ALA sources like flaxseed, chia, and walnuts to support overall fatty acid balance.
Discuss individualized needs and any testing options with your healthcare provider.

Diet Recommendations

Prioritize low-mercury fatty fish 2–3 times per week: salmon, sardines, trout, and anchovies are good choices.
If you do not eat fish, select a quality algae-based omega-3 supplement that supplies combined EPA and DHA — aim for at least 600 mg/day during pregnancy and lactation.
Include plant ALA sources such as flaxseed, chia seeds, hemp seeds, and walnuts for overall omega-3 variety and fiber, but do not rely on these alone if you have reduced conversion.
Balance omega-6 intake from vegetable oils and processed foods to support more favorable omega-3 status.

Supplement Recommendations and Practical Tips

Choose algae-based supplements if avoiding fish for dietary or ethical reasons. They provide direct DHA and some formulas include EPA.
Look for third-party tested products when possible to ensure purity and accurate dosing.
Take supplements as directed and discuss safety and dose with your healthcare provider, especially during pregnancy.
Consider taking omega-3 with a meal that contains fat to improve absorption.

Lifestyle and Monitoring

Discuss omega-3 testing with your clinician. Some providers can measure blood DHA or an omega-3 index to check status and guide supplementation.
Be mindful of mercury exposure: avoid high-mercury fish (shark, swordfish, king mackerel, tilefish) during pregnancy and lactation.
Maintain a balanced diet rich in whole foods, vegetables, lean proteins, and healthy fats to support overall maternal nutrition.
Keep healthcare appointments and review supplement use and dietary patterns with your prenatal care provider.

Summary

Your FADS2 genotype affects how well your body converts plant-based ALA into EPA and DHA. If you have AG or GG genotypes, you have reduced or low conversion and should prioritize direct sources of EPA and DHA during pregnancy and breastfeeding. Even with the AA genotype, pregnancy increases omega-3 needs, and direct sources are recommended. Practical steps include eating low-mercury fatty fish 2–3 times per week or taking a quality algae-based omega-3 supplement of at least 600 mg/day combined EPA and DHA when fish is not an option.

PlexusDx does not provide medical advice. This information is educational and about genetic predispositions only. Always consult with your healthcare provider before making changes to your diet, starting new supplements, or managing pregnancy health.