By Lawrence Goodman

updated 3:27 p.m. ET July 1, 2007

Money was tight, what with a baby boy in the house and another one on the way, so Teri Curtis cut costs. The 22-year-old bartender in Bentonville, Arkansas, saved on gas by making fewer trips to see her mother, who lived about an hour away. She and her husband stopped eating dinner out. And for lunch, she almost invariably had a plain tuna sandwich. “It was a cheap meal,” she remembers. “And I thought it would be nutritious.”

Curtis’s second son, Ryker, was born in June 2005, three weeks early. The doctors helicoptered him to a bigger hospital, where he was put in an incubator. The IV the nurses hooked up to his arm kept popping out every time he wriggled, so they inserted one through his scalp. Curtis was able to hold him for only a few hours a day. “On a scale of 1 to 10, I would say I was terrified at an 11,” Curtis says. “That poor kid.” It was a month before Curtis was able to take him home.

There were new problems, though. At 8 months, Ryker wasn’t responding to his name. And he didn’t look at Curtis when she talked to him.

It turned out that Ryker was nearly deaf. His adenoids, clusters of tissue toward the top of the throat, were swollen to the size of an adult’s, clogging up his hearing passageways. What the heck was going on with her child? Curtis wondered. She sat down with her ob/gyn, who ticked off some possible explanations. They could be seeing the health effects of Ryker’s prematurity. Or perhaps it was genetic.

But Curtis had heard something on the news that troubled her. Might mercury be a cause? “It’s unlikely, and we’ll never know for sure,” the doctor told Curtis. “But that might be it.” The toxin is found in certain varieties of seafood — including tuna, which Curtis had eaten at least three times a week for virtually her entire pregnancy. When a pregnant woman consumes mercury, it passes through the placenta into the brain of the fetus, where it can linger for years.

In extreme amounts, more than 10 micrograms per gram as measured in hair (which scientists use to gauge the body’s mercury levels), mercury can cause mental retardation, cerebral palsy, deafness and blindness. In the lower-level amounts typically found in Americans — fewer than 2 micrograms per gram in hair — risks to a newborn include a drop of a few IQ points, slow brain development and learning disabilities. Researchers at the U.S. Environmental Protection Agency estimate that more than 300,000 babies born each year in this country are at risk of having brain damage due to mercury exposure in utero.

Women may also have to worry for their own health: A 2003 study by San Francisco internist Jane Hightower, M.D., published in the journal "Environmental Health Perspectives," found that 89 percent of her female patients had mercury levels above what most scientists consider safe, and that high mercury levels in adults correlated with memory loss, fatigue and muscle aches. Another preliminary study this year found that mothers who delivered prematurely were more likely to have high mercury levels.

Even a suggestion, however remote, that her diet had played a role in Ryker’s illnesses left Curtis devastated. “I felt like everything my son was going through was my fault,” she says. But although she blamed herself, she couldn’t help but wonder why there were no warnings on the cans of tuna she ate. She hadn’t heard anything from the government about limiting tuna during pregnancy, nor did she recall her ob/gyn telling her that tuna might have mercury pollution. “This was something that should never have happened,” Curtis says. “I worry that it could have been prevented.”

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