Muka · Pregnancy guide
High-Mercury Fish to Avoid During Pregnancy
Updated June 2026 · based on NHS and official food-safety guidance
Mercury is a metal that builds up in large, long-living predator fish, and in pregnancy it can cross the placenta and harm your baby's developing brain and nervous system. The key rule: skip the few high-mercury species entirely, limit medium-mercury fish like tuna, and get your 2 to 3 weekly servings from low-mercury choices such as salmon, cod and shrimp. You don't need to give up fish, just choose the right ones.
Mercury is the one real reason to be choosy about fish in pregnancy. It collects in the water, fish absorb it, and big predator fish that eat smaller fish end up with the most, a form called methylmercury that crosses the placenta and can affect your baby's developing brain and nervous system. The good news is that the danger comes from only a short list of large species, not from fish in general. In fact the NHS, FDA, EPA and ACOG all want you to keep eating fish, because the omega-3s, iodine and protein in low-mercury types support your baby's development. This guide names the high-mercury fish to avoid during pregnancy, the ones to limit, and the safe choices to reach for, with both US and UK guidance so you can decide at the fish counter or restaurant in seconds. For a specific product, the Muka app gives you a verdict in 3 seconds by barcode scan or photo.
Fish sorted by mercury risk
| Fish | Verdict | Why |
|---|---|---|
| Shark, swordfish and marlin | Avoid | Among the highest-mercury fish of all. Both the NHS and FDA/EPA say avoid these completely in pregnancy, as mercury can damage your baby's developing brain and nervous system. |
| King mackerel, bigeye tuna, Gulf of Mexico tilefish, orange roughy | Avoid | All on the FDA/EPA "Choices to Avoid" list for high mercury, so skip them entirely while pregnant or trying to conceive. (For tilefish, only the Gulf of Mexico kind is on the avoid list; Atlantic tilefish is lower-mercury.) |
| Albacore (white) tuna and fresh tuna steaks | In moderation | Higher-mercury than canned light tuna. The FDA puts albacore in "Good Choices" at 1 serving a week; the NHS caps fresh tuna at 2 steaks weekly. Don't avoid, but don't overdo. |
| Canned light (skipjack) tuna | In moderation | Lower-mercury than steaks or albacore and a Best Choices fish, but still keep it within your weekly fish servings. The NHS allows up to 4 medium cans a week. |
| Salmon, cod, haddock, shrimp and sardines | Safe | All low-mercury Best Choices. Eat 2 to 3 cooked servings a week; they give your baby the omega-3s, iodine and protein that mercury worries can make people wrongly skip. |
| Tilapia, pollock, canned salmon, trout | Safe | Low in mercury and safe within your 2 to 3 weekly servings when fully cooked. Oily fish like trout still counts toward the NHS limit of 2 oily-fish portions a week. |
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Download Muka on the App StoreFrequently asked questions
Which fish are highest in mercury and must be avoided in pregnancy?
Avoid shark, swordfish, marlin, king mackerel, bigeye tuna, Gulf of Mexico tilefish and orange roughy. These large predator fish carry the most mercury, which can harm your baby's developing brain and nervous system. The NHS lists shark, swordfish and marlin; the FDA and EPA add the others to their "Choices to Avoid" list.
Why is mercury in fish dangerous during pregnancy?
Fish absorb methylmercury from water, and big predators build up the most. In pregnancy this mercury crosses the placenta and can interfere with your baby's developing brain and nervous system. The risk comes from regularly eating high-mercury species, which is why guidance targets only a short list of fish rather than fish in general.
Can I still eat tuna while pregnant?
Yes, within limits. Canned light tuna is lower-mercury and counts toward your 2 to 3 weekly fish servings; the NHS allows up to 4 medium cans a week. Albacore (white) tuna and fresh tuna steaks have more mercury, so the FDA allows 1 serving a week and the NHS caps fresh tuna at 2 steaks weekly.
How much low-mercury fish should I eat each week in pregnancy?
Aim for 2 to 3 servings (about 4 ounces or 113g each, so 8 to 12 ounces total) of low-mercury fish a week, say the FDA and EPA. The NHS frames it as up to 2 portions of oily fish weekly. Eating this much is encouraged, because fish supports your baby's brain and eye development.
I ate swordfish or shark before I knew I was pregnant. Should I worry?
Try not to panic. Mercury harm comes from eating high-mercury fish regularly over time, not from one meal. A single serving is very unlikely to cause problems. Just avoid these fish from now on, fill up on low-mercury choices instead, and mention it to your midwife or doctor if you're concerned.
Is canned tuna lower in mercury than a fresh tuna steak?
Yes. Canned light tuna is usually made from smaller skipjack tuna, which carry less mercury, so it's a Best Choices fish. Fresh tuna steaks and albacore (white) tuna come from larger fish with more mercury, which is why guidance limits steaks and albacore more tightly than canned light tuna.
Sources
- NHS — Foods to avoid in pregnancy: nhs.uk
See also: how Muka works, the pregnancy food scanner that answers “can I eat this while pregnant?”.