Fish and omega-3 in pregnancy: which fish are safe and how much?

When it comes to fish in pregnancy, you may hear two opposite messages: “Eat plenty” and “Stay away”. The truth sits in the middle. With the right choices, fish can be a valuable part of your pregnancy diet.

Why does omega-3 matter?

The omega-3 fatty acids in fish, especially DHA, play a role in the development of your baby’s brain and eyes. Fish also provides good-quality protein, iodine, vitamin D and selenium. Your need for these nutrients usually rises during pregnancy.

If you do not eat fish or simply do not like it, there is no need to worry. Omega-3 can come from other sources too, which we cover below.

The mercury question: it is the type of fish that matters

Some fish build up mercury as they move up the food chain. Large amounts of mercury are an unwelcome load for a baby’s developing nervous system. That is why big, long-lived predatory fish are generally not recommended in pregnancy.

Usually advised to avoid:

• Shark
• Swordfish
• King mackerel
• Marlin and similar large predators
• Bigeye tuna

Tuna is a little more nuanced: canned light tuna is generally considered low in mercury, while white (albacore) tuna and tuna steaks are limited to a certain weekly amount. You can ask your doctor or dietitian how often a particular product suits you.

Fish you can choose more freely

According to most health bodies, about 2–3 servings a week (roughly 300–350 grams in total) of low-mercury fish is a reasonable goal in pregnancy. This group includes:

• Salmon
• Anchovies and sardines
• Trout
• Sea bream and sea bass (farmed or from a known source)
• Cod, haddock and other white fish
• Thoroughly cooked shellfish such as prawns and mussels

Oily fish (salmon, anchovies, sardines) are rich in omega-3, so it is a good idea to include them in your weekly servings. For oily fish, the general advice is to stay at two portions a week; variety helps for both flavour and safety.

Cooking and hygiene

Safety depends on how fish is prepared as well as which kind it is.

• Cook fish thoroughly; the flesh should look opaque and flake easily with a fork.
• Sushi, raw fish, marinated fish and cold-smoked fish are generally not recommended in pregnancy because they can carry bacteria or parasites.
• When buying fish, look for freshness and a proper cold chain; keep any you do not eat right away in the fridge for a short time only.
• Wash chopping boards and knives that touched raw fish with hot water.

When you wonder whether a food is safe, you can also check the “Yenir mi?” feature in the app.

If you do not eat fish, where does omega-3 come from?

• Walnuts, flaxseed, chia and hemp seeds provide plant omega-3 (ALA). The body can convert a small part of ALA into DHA.
• Algae-based DHA supplements are an option for vegans and vegetarians.
• Some eggs are enriched with omega-3.

If you are thinking about a supplement, talk to your doctor first. Content and amounts vary, and products such as fish liver oil can be high in vitamin A, which is treated differently in pregnancy.

What you can do

1. Plan two fish days in your weekly menu, for example one oily and one white fish.
2. Check the name of the species when shopping; ask the seller if it is unclear.
3. Cook fish thoroughly and avoid eating it raw.
4. If there are local advisories (for lake or river fish caught nearby), check the latest notices.
5. If you do not enjoy fish, do not feel guilty; you can balance your diet with alternatives.

When to contact your doctor

• If you have severe vomiting, diarrhoea, fever or stomach pain after eating fish.
• If you think you accidentally ate raw or high-mercury fish and feel worried.
• If you have a fish or shellfish allergy, before trying a new type.
• If you are considering starting an omega-3 supplement.
• If you notice breathing difficulty or swelling of the lips or face, call 112 (your local emergency number) right away.

This article is for information only; your doctor’s or dietitian’s advice about your own diet comes first.