SATURDAY, April 11, 2009 (HealthDay News) -- Women who are pregnant should include fish in their diet for optimal maternal health and fetal growth and development. That much health experts agree on.
But just how much seafood moms-to-be can safely consume without exposing their unborn babies to dangerous levels of mercury is a matter of ongoing debate.
The U.S. Food and Drug Administration advises women to eat no more than 12 ounces a week, but a coalition of scientists in nutrition and medicine insists that expectant moms need at least that much.
"Recent data shows us that women are still not eating enough fish, and that's really alarming," said Judy Meehan, executive director of the National Healthy Mothers, Healthy Babies Coalition, an organization dedicated to disseminating the latest science on maternal and child health.
"There's simply no other way to get the omega-3s for brain development that you can from fish," she said.
Fish is packed with omega-3 fatty acids, a beneficial type of fat that is considered important for neural development.
Limiting fish intake to the government-recommended level, in fact, could be "detrimental" to a child's mental development, British and American researchers reported in 2007 in The Lancet. Their study found that children whose mothers ate at least three servings of fish a week during pregnancy performed better on tests of mental function.
In another study, Dr. Emily Oken, an assistant professor in the Department of Ambulatory Care and Prevention at Harvard Medical School and Harvard Pilgrim Health Care in Boston, examined the balance between the nutritional benefit and contaminant risk of consuming fish during pregnancy.
She and her colleagues asked 341 women about their fish consumption during the second trimester of pregnancy and tested their blood levels for mercury. When their children were 3, they took a battery of tests to assess intelligence and motor skills.
"Test scores were highest in children of mothers who ate more than two weeklyfish servings but had lower mercury levels, suggesting that the greatest benefit occurred when women ate fish low in mercury," Oken said.
"Even mothers who ate canned tuna more than twice weekly had children who scored better on tests, compared with those who did not eat canned tuna during pregnancy," she added.
Another study looked at 25,446 children born to Danish mothers. Kids whose moms ate more fish during pregnancy had better motor and cognitive test scores than those whose moms ate the least fish.
"Compared with women who ate the least fish during pregnancy, women who at the most fish -- about 14 ounces per week, on average -- had about a 30 percent likelihood of better development, about the same advantage a child would get from being one month older or from breast-feeding for more than one year," Oken explained.
The National Healthy Mothers, Healthy Babies Coalition partnered with the Maternal Nutrition Group, an independent group of physicians, researchers and nutritionists, in 2007 to encourage pregnant women to eat fish as part of a healthy diet. The concern was that many women were interpreting the FDA guidelines as a warning and curtailing their fish intake.
The FDA advisory, first issued in 2004, targets women who are pregnant or may become pregnant as well as nursing mothers and young children. These populations are urged to avoid certain types of fish that may be higher in mercury and therefore toxic to a baby's or child's developing nervous system. These include shark, swordfish, king mackerel and tilefish.
The FDA suggests choosing varieties lower in mercury and eating no more than 12 ounces -- or roughly two meals -- of fish or seafood a week. That upper limit should include no more than 6 ounces of albacore tuna a week, it says.
The American College of Obstetricians and Gynecologists echoes that advice in its own nutritional guidance.
Still, many Americans, including expectant moms, don't get even two servings a week.
"The message is, eliminating fish is not a good thing," Meehan said. "Fish is uniquely important for brain development in babies."
The American Pregnancy Association has more on mercury levels in fish.