Fish in Pregnancy: Which Ones Are Safe, Which to Avoid, and Why
A practical guide to knowing which fish you can eat while pregnant, which to avoid because of mercury, anisakis or listeria, and how often to eat them according to AESAN and the WHO.
Fish is one of the most recommended foods during pregnancy. It provides high-quality protein, iodine, vitamin D and omega-3 fatty acids, which are essential for the development of the baby’s brain and eyes. But not all fish are equal: some contain high levels of mercury, and others may carry parasites or bacteria that are dangerous to the fetus.
This guide summarizes, following the recommendations of the AESAN (Spanish Agency for Food Safety and Nutrition) and the WHO, which fish you can eat without worry, which ones should be limited, and which to avoid completely throughout the nine months.
Why fish matters during pregnancy
During pregnancy, the baby’s brain and nervous system need a constant supply of DHA, a type of omega-3 found mainly in oily fish. Iodine (key for cognitive development) and vitamin D are also needed.
The AESAN recommends eating 3 to 4 servings of fish per week, combining white and oily fish. Cutting fish out entirely is not a good idea: you would miss nutrients that are hard to get from other sources.
The problem: mercury, anisakis and listeria
There are three specific risks that justify these precautions:
- Mercury: it accumulates in large, predatory fish. It can affect the neurological development of the fetus.
- Anisakis: a parasite found in raw or undercooked fish. It causes allergic and digestive reactions.
- Listeria: a bacterium that survives in smoked, marinated or raw fish. It can cross the placenta and cause serious complications.
The good news: all three are easy to control by choosing the right species and cooking the fish to above 60 °C, or freezing it beforehand if it is to be eaten raw.
Fish you CAN eat (3-4 times per week)
These are low in mercury. You can eat them with confidence, always well cooked:
- Sardine, anchovy, Atlantic mackerel, horse mackerel
- Hake, whiting
- Cod
- Sole, John Dory
- Salmon (cooked, not smoked or raw)
- Trout
- Turbot, sea bream, sea bass
- Anchovy (fresh, cooked)
- Squid, cuttlefish, octopus
- Mussel, clam, cockle (well cooked)
These fish offer both safety and good nutritional value. Alternate white fish (lean and easier to digest) with oily fish (richer in omega-3).
Fish to eat with caution (1-2 times per month at most)
They contain moderate levels of mercury. The AESAN allows them in limited amounts:
- Albacore tuna
- Monkfish
- Scorpionfish
- Bluefish
An occasional serving is not a problem, but these should not be your regular fish during pregnancy.
Fish you should NOT eat during pregnancy
The AESAN is clear: during pregnancy, breastfeeding and for children under 10, these fish must be avoided completely because of their high mercury content:
- Swordfish
- Bluefin tuna (Thunnus thynnus, the large one)
- Shark (dogfish, mako, blue shark, porbeagle)
- Pike
Canned light tuna is permitted in moderation (it is a smaller species with less mercury).
Raw, smoked and marinated fish: best avoided
Here the problem is not mercury but anisakis and listeria. During pregnancy, avoid:
- Sushi, sashimi, ceviche, homemade vinegar-marinated anchovies or any that have not been guaranteed to have been frozen beforehand
- Smoked salmon, smoked trout, smoked cod
- Fish carpaccio
- Raw oysters and other uncooked shellfish
- Surimi of poor quality with no storage guarantees
If you really crave sushi, there are cooked options (tempura, eel) or vegetarian ones you can enjoy without risk.
How to cook fish to eliminate risks
Two simple rules and everything is covered:
- Cook to above 60 °C at the center of the piece. No pink spots or lukewarm sushi. Baked, grilled, steamed, stewed or fully fried.
- If you are going to eat it raw, marinated or undercooked (although not recommended during pregnancy), it must have been frozen at -20 °C for at least 5 days.
Homemade vinegar-marinated anchovies are one of the biggest sources of anisakis in Spain. If you prepare them yourself, freeze the fish beforehand without exception.
Benefits of omega-3 during pregnancy
DHA contributes to the baby’s brain and visual development, especially in the third trimester, when the greatest neuronal growth occurs. It has also been associated with a lower risk of preterm birth.
The best sources are small oily fish: sardine, anchovy, mackerel, salmon. Two weekly servings of oily fish more than cover the needs. If you don’t eat fish, talk to your midwife: they may consider an algae-based DHA supplement.
Looking after your diet goes hand in hand with other important habits at this stage, such as safe amounts of coffee, tea and herbal infusions, where there are also nuances worth knowing.
Frequently asked questions
Can I eat canned tuna during pregnancy? Yes, canned light tuna comes from small species (skipjack, yellowfin) with low mercury levels. You can eat it normally within your weekly fish servings. Bluefin tuna, however, is not recommended.
Is smoked salmon from the supermarket safe if it’s packaged? Not during pregnancy. Even if it is vacuum-packed, cold smoking does not eliminate listeria. You can eat it if you cook it (for example, in a very hot pasta dish).
And prawns and langoustines? Yes, always well cooked. Avoid cold seafood cocktails if you have no storage guarantees, and discard heads and dark parts of shellfish, where cadmium is most concentrated.
Is there a problem if I ate swordfish before I knew I was pregnant? Don’t panic. The risk from mercury is cumulative. A one-off intake before you knew about the pregnancy is not a problem. From now on, replace it with safe options.
Can I eat frozen fish? Yes, and it is actually a very safe option: industrial freezing kills anisakis. Just make sure you cook it well.
For any specific doubts about your diet during pregnancy, your midwife or gynecologist are best placed to advise you according to your situation.
