For years, pregnant and nursing women have been warned to limit the amount of fish they eat, because many marine species may contain high levels of mercury, which endangers newborns and fetuses. Yesterday, however, a children’s health group challenged the conventional wisdom, advising pregnant women and nursing mothers to eat more fish so as to ensure optimal brain development in their babies.Fearing mercury contamination, many pregnant women avoid seafood altogether. That may actually harm newborns, according to some scientists. (John McConnico for The New York Times) What’s going on here? Currently, the Food and Drug Administration advises pregnant women to limit their weekly seafood consumption to no more than 12 ounces, or about two servings, per week. The newest recommendation comes from the National Healthy Mothers, Healthy Babies Coalition, a nonprofit group that focuses on childhood health issues. That group’s scientific advisors say that pregnant women and nursing mothers should eat at least 12 ounces of fish per week. Although both recommendations acknowledge that pregnant women can safely eat about two servings a week, fears of mercury contamination in seafood have prompted many pregnant women to forgo fish entirely. And here’s the conundrum: an increasing number of studies indicate that omega-3 fatty acids, found mostly in fish, are essential to brain development in fetuses and newborns. Earlier this year, a report in The Lancet, a medical journal, concluded that women who had eaten more than 12 ounces of fish per week during pregnancy produced better developed, more intelligent children. “Advice that limits seafood consumption might reduce the intake of nutrients necessary for optimum neurological development,” wrote scientists from the National Institutes of Health and the University of Illinois at Chicago.“The real problem here are the women who are just eliminating fish from their diet,” said Judy Meehan, executive director of the National Healthy Mothers, Healthy Babies Coalition. “Eating 12 ounces is a very safe, smart move, and nobody is disputing that.'’ While none of the research cited yesterday in the coalition’s recommendations has been funded by the fish industry, the coalition is using a grant from the National Fisheries Institute, a seafood industry group, to fund its educational campaign, according to Ms. Meehan.