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Pregnant Moms Getting Fishy Advice

Fishy Warnings

A Rock and a Hard Place

Knowing that it's risky to eat too much contaminated fish doesn't help women out of the quandary they're in, however. Just as mercury from fish can damage a baby's developing nervous system, some evidence shows that not eating enough fish may be harmful, too. Danish researchers reported in a February issue of the British Medical Journal that women who ate too little fish had a higher risk for premature delivery than women who ate a lot of fish did. The women who ate less fish also had a higher risk for having babies with low birth weight.

"Fish is an excellent source of nutrition, especially for pregnant women," says Daniel Lasser, MD, director of obstetric services at the Weill Cornell School of Medicine in New York. Some fish (like Pacific salmon, farmed catfish, and farmed trout) are nutritious and have very little mercury, but Lasser says he thinks tuna is particularly important because it's so popular and readily available. "I'm often asked about tuna," he says.

Chapin says the FDA may be underestimating how much tuna women eat: It's low in saturated fat; it's high in protein and omega-3 fatty acids; and it's cheap. "It's kind of a lifestyle-choice food," she says.

Lasser says he thinks public health advisories can go a long way toward preventing problems in the womb. For example, the push to get women to take folic acid supplements during pregnancy has led to a drop in cases of spina bifida (a spinal birth defect) in the U.S. But he says that trying to prevent exposure to toxins from otherwise healthy food is far more complicated.

How Much Is Too Much?

The FDA's safety limit for mercury in fish is 1 part per million (ppm). Samples of shark, king mackerel, swordfish, and tilefish that the FDA tested all had an average of about 1 ppm. Tuna steaks had an average of 0.32 ppm, and canned tuna had only 0.17 ppm.

But the EWG claims that FDA limits are too lax, and that many women eat enough tuna and other fish to raise the amount of mercury in their bodies to dangerous levels. They point to a study from the CDC showing that 10% of American women are very close to having enough mercury in their bodies to put their babies at risk, were they to get pregnant.

The Environmental Protection Agency's method for setting limits on mercury levels is different from the FDA's. The EPA limit, which is also endorsed by the National Academy of Sciences, allows up to 0.1 micrograms per kilogram of a person's body weight per day. The EWG claims that's eight times more protective than the FDA's limit.

But Lasser says he thinks none of the data the government agencies are going on is completely sound. "There's a great deal of uncertainty and lack of knowledge" about how much mercury is safe to eat, he says. "We don't know the half of it."

He says he warns his patients about the risks of eating fish, but he also tells them about the benefits. Lacking precise scientific data on how much is too much, he says, "How crazy you're going to get about it becomes a matter of personal choice."

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