Can I eat mussels while pregnant?

The verdict

It splits cleanly on two axes: cooked versus raw, and which country you are in.

Cooked mussels are safe under UK advice. The NHS lists cooked shellfish, including prawns, crab, lobster, squid, mussels, scallops, clams and cockles, among foods that are safe to eat in pregnancy. The FDA's instruction is to cook clams, mussels and oysters until their shells open, which means they are done, and to throw away the ones that did not open.

Raw oysters are out everywhere. The NHS lists raw shellfish among foods to avoid. ACOG advises avoiding all raw and undercooked seafood. The FDA states that a pregnant woman and her unborn baby are at risk if she eats raw or undercooked seafood, and that moms-to-be should avoid raw or undercooked finfish or shellfish, including oysters, clams, mussels and scallops. FSANZ names raw oysters in its higher-risk group.

Ireland is the outlier. The HSE lists clams, oysters, scallops, prawns and mussels among foods to avoid in pregnancy, adding that the risk is highest if they are pre-cooked. That reads as a blanket avoid rather than a raw-only restriction.

Why molluscs are treated differently from fish

Mussels, oysters, clams and scallops are filter feeders. The FDA explains the consequence: clams, mussels and other molluscs get their food by filtering large quantities of water through their shells, and in doing so they can accumulate more bacteria and viruses than finfish, which makes raw molluscs particularly unsafe to eat.

The NHS adds the specific organism most people encounter. Raw shellfish, particularly oysters, can contain low levels of certain viruses such as norovirus, and shellfish such as mussels, clams and oysters that are raw or not thoroughly cooked can contain harmful viruses and bacteria that cause food poisoning. Thorough cooking usually kills them.

None of that is a pregnancy-specific hazard in itself. It becomes one because ordinary food poisoning is worse in pregnancy: dehydration is riskier, and ACOG notes that vomiting and diarrhoea can cause the body to lose too much water, which can be dangerous for you and your fetus.

Shellfish toxins, which cooking does not fix

This is the part that is genuinely different from every other food on this site. The NHS states that shellfish can also contain toxins, that symptoms may include nausea, vomiting, diarrhoea, headaches, numbness, breathing difficulties, memory loss, disorientation and abdominal pain, and that these toxins do not break down during cooking.

Shellfish toxins come from algae the molluscs filter out of the water, and they are heat-stable. Commercial shellfish beds are monitored and closed when toxin levels rise, which is why buying from a proper supplier matters more here than with almost any other food, and why gathering your own mussels from a beach is not a good idea in pregnancy.

Cooking mussels properly

The FDA's test is the shells. Cook clams, mussels and oysters until their shells open; that means they are done, and the ones that did not open should be thrown away. For shucked clams and oysters, the test is that they are fully cooked when they are opaque, milky white and firm.

A pot of moules mariniere cooked until the shells gape, mussels in a hot pasta sauce, a seafood stew brought to a simmer, and oysters baked or grilled all clear the bar. Mussels that are still tightly closed after cooking should be discarded, not prised open.

Cold cooked mussels are a separate question. A chilled seafood salad, a jar of pickled mussels or mussels on a cold platter are ready-to-eat chilled foods, and the FSA lists cooked shellfish among the ready-to-eat foods where listeria is more commonly found. FSANZ places chilled ready-to-eat seafood in its higher-risk row and offers freshly cooked or thoroughly reheated to steaming hot as the alternative.

Oysters specifically

Raw oysters are the highest-risk item in this whole group, and they are also the one most people are asking about, because oysters are normally served raw.

The NHS notes that most of the shellfish we eat is cooked first, but oysters are often served raw, and that if you are serving oysters raw you should be especially careful when buying and storing them. For pregnancy, the answer is simpler: raw shellfish is on the avoid list.

Cooked oysters are a different food. Oysters Rockefeller, grilled oysters, oysters in a pie, and steamed oysters are all cooked. FSANZ's higher-risk entry names raw oysters, and the FDA's warning covers raw or undercooked, so oysters that have been properly cooked through are not caught by either.

On mercury, oysters are not a concern at all. The FDA places oyster on its Best Choices list, and names oysters among the fish even lower in mercury.

Mussels and iron

There is a reason to want mussels in pregnancy rather than merely to tolerate them. Mussels are a dense source of iron, iodine, selenium, zinc and vitamin B12, and the NHS notes that mussels, oysters, squid and crab are also good sources of long-chain omega-3 fatty acids, though not as much as oily fish.

Iron requirements rise in pregnancy, and iron from shellfish is well absorbed. If you like mussels and cook them thoroughly, they are a useful food, not merely a permitted one. In Ireland, where the HSE asks pregnant women to avoid them, oily fish within the two-portion limit and lean red meat cover the same nutrients.

If you have already eaten some

If they were cooked, there is nothing to do outside Ireland, and even there the advice is a precaution rather than a warning about a specific incident.

If you ate a raw oyster, watch for ordinary food poisoning symptoms over the next day or two: nausea, vomiting, diarrhoea and stomach cramps. NHS advice is to get help from 111 if you feel unwell after having food that should be avoided in pregnancy, or if you have had vomiting and diarrhoea for more than 48 hours. If you get numbness, tingling around the mouth, breathing difficulty or disorientation, that suggests a shellfish toxin rather than an infection and needs urgent medical attention.

Listeria is less likely from cooked shellfish than from chilled ready-to-eat food, but if fever, chills, muscle aches, headache or a stiff neck appear in the following weeks, contact your midwife or GP and say what you ate.

Where guidance genuinely differs

The UK, US and Australia all draw the line at raw. Cook the mollusc, and it comes off the restricted list.

Ireland draws it at the food. The HSE names clams, oysters, scallops, prawns and mussels outright, with the note that the risk is highest if they are pre-cooked, which suggests the concern there is chilled ready-to-eat shellfish rather than shellfish as such, but the list as published does not carve out freshly cooked mussels.

If you are in Ireland and want to follow the guidance as written, skip them. If you are elsewhere, cook them until the shells open, buy from a reputable supplier, and eat them hot.