For the last decade, federal officials have recommended a maximum amount of fish that pregnant and nursing women should consume.
Recently, they proposed setting a first-ever minimum, basing it on studies that showed these women weren't eating enough fish.
The Food and Drug Administration and the Environmental Protection Agency teamed up for the new recommendation, that women in this group eat eight to 12 ounces of seafood - or two to three servings - a week.
They said young children also should eat two to three servings a week, with portions adjusted to the child's age and size.
The chief benefit: Eating fish is good for brain development and can boost a child's IQ, officials said.
The caveat: The fish should be varieties that are typically lower in mercury - one reason many women avoid fish. Mercury is a neurotoxin that, among other things, can impair neurological development.
"For years, many women have limited or avoided eating fish during pregnancy or feeding fish to their young children," said Stephen Ostroff, the FDA's acting chief scientist.
An FDA analysis of seafood consumption by 1,000 women in the United States found that about a fifth of them had eaten no fish in the previous month. Among those who did, three-quarters ate less than four ounces a week - half of the minimum now recommended.
"The information that's been developed over the past decade strongly demonstrates that the health benefits that accrue from the consumption of fish far outweigh any risk," Ostroff said.
The agencies recommended salmon, shrimp, pollock, canned light tuna, tilapia, catfish, and cod. These are among the top 10 seafood species consumed in the U.S., according to the National Marine Fisheries Service.
The agencies said four high-mercury fish - tilefish from the Gulf of Mexico, shark, swordfish, and king mackerel - should be avoided. And they said women and children in the target group should eat no more than six ounces of albacore tuna a week.
The proposed guidelines are subject to change, following a public comment period.
The National Fisheries Institute, a seafood industry group, praised them. Jennifer McGuire, an Institute nutritionist, called them "a great starting point for encouraging women to eat more seafood for the health benefits."
Critics say the guidelines are not specific enough, and not protective enough.
The Mercury Policy Group, an advocacy group that sued the FDA this year seeking fish labeling requirements, said consumption of albacore tuna should be more strongly discouraged.
The Environmental Working Group, a national nonprofit, said the agencies should have highlighted more clearly the species of fish with the most omega-3 fats, which are the brain boosters and have other healthful effects.
The group found that the best seafood choices, providing both beneficial fats and low mercury risk, are salmon, sardines, farmed trout, anchovies, shad, herring, and mussels.
The EWG found that some of the seafood the agencies recommend - shrimp, tilapia, and catfish - are actually low in omega-3 fats.
The groups also suggested labels as a way to steer consumers toward the best choices.
PROPOSED FISH GUIDELINES
Recommended amount: 8 to 12 ounces - two to three servings - per week for women who are pregnant, might become so, or are breast-feeding.
For children: Two to three servings a week, with the amount based on the child's age and size.
Choose low-mercury fish: Including salmon, shrimp, pollock, light canned tuna, tilapia, catfish, cod.
Avoid: Tilefish from the Gulf of Mexico, shark, swordfish, king mackerel. Limit albacore tuna to six ounces a week.
Fish from streams, rivers, or lakes may have other contaminants. Check fish consumption advisories.
For Pennsylvania: http://tinyurl.com/q5movas
For New Jersey: http://tinyurl.com/p9gwtej
More on the proposal: http://tinyurl.com/ptuslve
SOURCE: U.S. FDA and EPA.
"GreenSpace," about the environment and health, appears every other week, alternating with Art Carey's "Well Being" column.