They ate fish during pregnancy – lots of it. Their children are now teenagers and show no signs that their high levels of mercury exposure while in the womb led to any problems with intellectual development.

“Everyone on this team was so sure that we would find adverse effects from high levels of mercury,” said Philip W. Davidson, professor of pediatrics, environmental medicine and psychiatry at the University of Rochester School of Medicine and Dentistry. “It was a shock. We didn’t believe it. The kids are almost 16 and we still have yet to see a problem.”

Davidson’s work was presented at the American Association for the Advancement of Science meeting in St. Louis. He and colleagues from the Ministry of Health in Seychelles have been following 770 children whose mothers were tested during pregnancy for their exposure to mercury from fish. Women from this group of islands in the western Indian Ocean consume 10 times the fish that Americans do.

The study was designed to test the effects of mercury on the developing fetus and then follow the child to see if it affected development. The concern was born in the 1950s when a factory in Japan dumped high levels of mercury in the water, which led to children born with developmental abnormalities. This was an acute poisoning from massive levels of mercury, but it left open another question: Can low level, chronic mercury exposure be harmful to the developing fetus?

“This is good news,” said Conrad Shamlaye, an epidemiologist with the Ministry of Health in Seychelles. “If people ate 10 times the level of fish with no problem, then Americans should not worry about consuming fish.”

There continues to be controversy over mercury exposure – both from fish and from man-made pollutants. The Food and Drug Administration has studied the issue and has tried to educate the public about the importance of the nutrients in fish while trying to minimize exposure to mercury.

Many environmental groups have advised that pregnant women and children younger than 6 limit their intake of canned tuna, fresh tuna, swordfish and shark. These environmentalists say the FDA’s evaluation program for mercury contamination is inadequate.

Mercury enters the atmosphere and drops into lakes, streams, rivers and oceans. But about 85 percent of the mercury pollution in the United States is caused by power plants that burn coal and incinerators that burn trash that contains mercury.

The Rochester group has continued to conduct neuropsychological tests on these children.

“We have seen problems in other studies,” said Jason Babbie, a senior environmental policy analyst for the New York Public Interest Research Group. “It is incumbent to act on the side of caution.”

Davidson said that there could be several explanations for the surprising findings. For one thing, the amount of mercury consumed from fish “may be just too low to cause problems,” he said. This study found high levels of mercury in tests of the mothers’ hair, a good indicator of what both mothers and fetuses were exposed to. Another possibility: Fish may contain micronutrients that support the developing brain and prevent the potential problems of mercury exposure.

The team has been doing another study in the same region on another group of pregnant mothers and their children, who are now about 4. In addition to studying mercury levels, they also studied the blood for other nutrients from fish, including omega-3 fatty acids, omega-6 fatty acids, taurine, choline and protein.