Mercury in Fish During Pregnancy

The FDA and EPA jointly publish seafood guidelines for pregnant women, dividing fish into three categories based on mercury levels. Here's how to use them:

Best Choices (2-3 servings per week): These fish have the lowest mercury levels. This includes shrimp, salmon, sardines, tilapia, cod, catfish, pollock, anchovies, and canned light tuna (skipjack). Build most of your seafood intake from these.

Good Choices (1 serving per week): Moderate mercury levels. Includes albacore (white) tuna, halibut, snapper, mahi mahi, crab, lobster, grouper, and sea bass. These are safe but should be eaten less frequently.

Choices to Avoid: The 7 highest-mercury species listed above should be avoided entirely during pregnancy. These are large, long-lived predatory fish at the top of the marine food chain, where mercury bioaccumulates to dangerous levels.

For a complete overview of food safety, see our complete food safety guide.

Mercury enters waterways from both natural sources (volcanic activity, erosion) and human activity (coal-burning power plants, mining). In water, bacteria convert mercury into methylmercury, which is absorbed by small organisms and bioaccumulates up the food chain — each predator concentrating the mercury from everything it eats.

Methylmercury crosses the placenta efficiently. In the developing fetus, it affects the brain and nervous system. High prenatal mercury exposure is associated with reduced cognitive function, impaired fine motor skills, attention deficits, and speech and language delays.

The critical point: the risks are dose-dependent and cumulative. Eating a single serving of high-mercury fish is unlikely to cause harm. The concern is consistent, repeated exposure over the course of pregnancy. This is why the guidance focuses on weekly consumption patterns rather than individual meals.

Equally important: fish contains DHA omega-3 fatty acids that are essential for fetal brain development. Studies consistently show that children whose mothers ate low-mercury fish during pregnancy have better cognitive outcomes than those whose mothers avoided fish entirely. The goal is not to fear fish — it's to choose wisely.

The simplest strategy: stick to the "Best Choices" list for most of your seafood. Shrimp, salmon, sardines, and canned light tuna are affordable, widely available, and among the lowest-mercury fish. Two to three servings per week from this category is both safe and beneficial.

When eating out, avoid ordering shark, swordfish, or marlin — these are sometimes featured as specials at restaurants. If a menu lists a fish you're not sure about, ask how it's prepared and check the FDA list.

For sushi lovers, cooked rolls are your friend. See our sushi during pregnancy guide for safe options. For detailed information on specific seafood, check our guides on tuna, crab, and lobster.

For local catches (recreational fishing), check your state's fish advisories at the EPA's website. Local waterways may have specific contamination that makes certain fish higher in mercury or other pollutants than the national averages suggest.

This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.