Rethinking the guidelines
The federal government's guidelines are designed to ensure that women avoid getting too much mercury, but recent studies show that the amount of seafood recommended may be too low to confer maximum benefits to babies. One such study, headed by Oken, looked at fish intake among more than 2,000 pregnant women.
"We did developmental testing on their children at ages 6 months and 3 years and found that the women who ate more than two servings of seafood per week—more than 12 ounces—had better outcomes related to IQ, as well as fine-motor, visual-motor and visual-spatial skills," says Oken.
Another study, reported in February 2007, found that among almost 12,000 pregnant women, those who had a seafood intake of less than 340 grams per week (equivalent to 12 ounces) had children who were more likely to be in the lowest range for verbal IQ scores. Low intake was also linked to poorer fine-motor, communication and social-development skills in the children, who ranged in age from 6 months to 8 years. "For each outcome measure, the lower the intake of seafood during pregnancy, the higher the risk of suboptimum developmental outcome," the study reported.
And certain types of seafood are more beneficial than others. "If a woman is eating 12 ounces per week of the oilier, darker, fattier fish, she's probably getting enough DHA," Mozaffarian says. "But if she's eating the same amount of white fish, she's probably not."
Alternatives to fish
Whether it's because they fear mercury or simply don't like seafood, some pregnant women wonder whether fish oil supplements can take the place of fish. Experts seem divided on the issue. Mozaffarian, for instance, says fish oil capsules "certainly have DHA" and are a reasonable alternative.
Myers prefers that women get their DHA from food sources. "Seafood contains more than just long-chain fatty acids," he explains. "It has high-quality protein and many other important nutrients that you might or might not get by simply taking a supplement." (Myers also points out that some other foods—walnuts, flax seed, enhanced eggs and grapeseed oil, for example—contain omega-3s.)
If you're concerned that fish oil supplements might contain mercury, be aware that a 2004 test conducted by consumerlab.com showed that none of the 42 brands tested were contaminated with the toxin. (Fish oil supplements are not studied by the FDA.) What's more, a study published in the February 2007 issue of the European Journal of Clinical Nutrition found that among pregnant women with previous pregnancy complications—including preterm delivery, pregnancy-induced hypertension or intrauterine growth retardation—fish oil supplementation delayed the onset of delivery in the women with low or medium fish intake.
And if you're interested in the recent influx of foods with added omega-3s, be certain to read labels. "If you're going to rely on these foods to supply omega-3s, make sure they have DHA or EPA—or, even better, the combination," Mozaffarian advises. (ALA, another common omega-3, is not as beneficial for fetal development.) Daily Values have not been established for omega-3s and therefore may not be listed on a food's nutrition information label. Instead, most foods containing added omega-3s tout this elsewhere on the product packaging.
So what does all this information boil down to? Experts recommend the following:
• Follow the government's guidelines on the four types of fish to avoid entirely during pregnancy.
• Focus on smaller, darker, fattier types, which tend to have the highest amounts of omega-3s.
• To provide optimal benefits for your baby, consider eating more than the recommended 12 ounces per week. "The vast majority of seafood has almost undetectable amounts of mercury," says Mozaffarian, "so you can eat at least two servings a week of a variety of species and have no concern about contamination." However, he also recommends that people who consume five or more servings per week focus on varieties with the lowest mercury levels. (See "The Perfect 10?".)
Also keep in mind these words from Mozaffarian: "The key message is that there is some evidence of subtle danger to babies and infants from too much mercury, but there's even more consistent evidence of at least as much neurological danger from their mothers eating too little seafood."