Omega-3 During Pregnancy: Why It Matters

Quick Answer

Omega-3 fatty acids—specifically DHA (docosahexaenoic acid)—are genuinely important during pregnancy. DHA is a primary building block of your baby's brain and eyes, with research showing it plays a fundamental role in neurological development. Pregnant women should aim for at least 200-300 mg of DHA per day, ideally through 2-3 servings of low-mercury fatty fish weekly or via supplements.

This guide covers everything you need to know: what omega-3s are, why DHA matters so much, the best food sources, mercury safety, and whether you need supplements.

What Are Omega-3 Fatty Acids?

Omega-3s are polyunsaturated fats classified as "essential"—meaning your body cannot produce them. You must get them from food or supplements. There are three main types:

Key point: When we talk about omega-3s during pregnancy, we're primarily talking about DHA.

Why DHA Is Critical During Pregnancy

DHA makes up approximately 40% of the polyunsaturated fatty acids in the brain. During the third trimester and first two years of life, your baby's brain undergoes explosive growth—and DHA is essential for forming cell membranes in neural tissue.

A landmark study in The American Journal of Clinical Nutrition found that children whose mothers had higher DHA levels during pregnancy showed improved problem-solving abilities at 9 months of age.

How Much Omega-3 Do You Need?

Recommendations from leading health organisations:

Practical takeaway: Aim for at least 200-300 mg of DHA per day during pregnancy.

Best Food Sources of Omega-3 (DHA + EPA)

The most efficient way to get DHA and EPA is through fatty fish. Plant sources provide ALA but aren't reliable for meeting DHA needs.

Fatty Fish (Top Tier)

• Salmon (wild or farmed): 100g = 1,500–2,000 mg DHA+EPA — Excellent choice, low mercury
• Sardines: 100g = 1,400–1,800 mg — Very low mercury, eat with bones for calcium
• Anchovies: 100g = 1,200–1,500 mg — Small fish = low mercury
• Mackerel (Atlantic): 100g = 1,000–1,400 mg — Choose Atlantic over King mackerel
• Herring: 100g = 1,300–1,700 mg — Great smoked or pickled
• Trout (rainbow): 100g = 800–1,000 mg — Farm-raised often available

Two servings per week of low-mercury fatty fish can easily meet your omega-3 needs.

Plant Sources (ALA Only)

These provide ALA but conversion to DHA is too low to rely on solely:

• Flaxseeds (ground): 1 tbsp = 1,600 mg ALA
• Chia seeds: 1 tbsp = 1,700 mg ALA
• Walnuts: 30g = 2,500 mg ALA
• Hemp seeds: 1 tbsp = 1,000 mg ALA

Mercury Safety: Navigating Fish Choices

Mercury is a valid concern—but avoiding fish entirely is the wrong approach. The benefits of omega-3s generally outweigh mercury risks when you choose wisely.

The NHS and FDA recommend pregnant women eat 2–3 servings (about 8–12 ounces) of low-mercury fish per week.

Omega-3 Supplements: When and What to Take

If you don't eat fish regularly—or at all—supplementation becomes important.

Who Should Consider Supplements?

• Vegetarians and vegans
• Women who dislike fish or have allergies
• Anyone not eating 2+ servings of fatty fish weekly
• Women with history of preterm birth (higher doses may be recommended)

Types of Supplements

• Fish oil: High DHA+EPA, widely available, affordable. May cause fishy burps.
• Algae oil: Vegan-friendly, sustainable, directly provides DHA. Often lower EPA.
• Cod liver oil: Contains vitamin A+D. Avoid high doses due to vitamin A.
• Krill oil: Good absorption, contains astaxanthin. Lower total omega-3 per capsule.

What to Look For

• At least 200-300 mg DHA per serving (check label—total omega-3 isn't the same as DHA)
• Third-party tested (IFOS, NSF, or USP certifications)
• Triglyceride form (better absorbed)
• No strong fishy smell (indicates freshness)

Knowledge Check

Common Questions

• Can I get enough from plant foods alone? Not really. Flaxseeds and walnuts provide ALA, but conversion to DHA is under 5%. Vegans should supplement with algae DHA.
• Will fish oil supplements make me burp fish? Some lower-quality ones can. Freeze capsules, take with food, or try algae oil.
• Is it possible to have too much omega-3? Very high doses may affect blood clotting. Stick to under 1,000 mg DHA+EPA combined unless advised by your doctor.
• Should I stop before delivery? Some practitioners recommend stopping high-dose supplements 2 weeks before due date. Discuss with your provider.
• Do omega-3s pass through breast milk? Yes! Continue adequate intake during breastfeeding to support ongoing brain development.

The Bottom Line

Omega-3 fatty acids—particularly DHA—are genuinely important during pregnancy. They support your baby's brain and eye development, may reduce preterm birth risk, and benefit maternal mental health. Aim for 2-3 servings of low-mercury fatty fish per week, or supplement with fish oil or algae-based DHA if fish isn't in your diet.

Every salmon fillet is a small investment in your baby's future brain development. Trust your body, feed it well.

Related Reading

See also: Calcium in Pregnancy, Iron in Pregnancy, Is Salmon Safe in Pregnancy?, and Can I Eat Tuna While Pregnant?.

Download PregnancyPlate to track your omega-3 intake, check fish mercury levels instantly, and ensure you're meeting key nutrient targets throughout pregnancy.