Fish consumption in pregnancy and fetal risks of methylmercury toxicity.

QUESTION: Because I practise in a rural area with a large number of lakes, I have patients planning pregnancy who consume relatively large amounts of fish harvested by their families. What should be my advice to them?

ANSWER: A recent Motherisk study has shown that fairly commonly these women's mercury levels exceed the threshold level for cognitive effects. Women should not consume excessive amounts of seafood in pregnancy (ie, no more than 2 weekly average size servings). Hair mercury level above 0.3 μg/g indicates a potentially excessive body burden.