You might not have believed your mother when she told you that eating fish would make you smarter, but according to a new study, if she ate seafood while pregnant, your IQ might have increased.

Last week, a team of researchers led by a professor at Harvard Medical School (HMS) published a scientific paper stating that mothers who eat seafood during pregnancy have smarter children.

The study, published in the October issue of the peer-reviewed journal Environmental Health Perspectives, is a new wrinkle in the debate over the safety of fish consumption for pregnant women.

Currently, the Food and Drug Administration (FDA) recommends that pregnant women limit their seafood intake to two servings per week.

FDA guidelines say that some types of fish, such as shark, swordfish, and king mackerel, contain high levels of mercury, which has been shown to cause nervous system defects and occasional death in infants.

“For most people, the risk from mercury by eating fish and shellfish is not a health concern,” states a March 2004 FDA report. “Yet, some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child’s developing nervous system.”

But HMS Professor Emily Oken, who spearheaded the Environmental Health Perspectives study, said the risks of eating fish while pregnant must be weighed against the benefits.

“Over the last few decades there’s been a lot of scientific evidence suggesting that experience in early life can have a long term influence on later childhood disease,” she said. Oken hypothesized that the link between fish consumption and intelligence is based on previous research suggesting that omega-3 fatty acids, which are abundant in seafood, are linked to neurological development.

Oken’s team concluded that seafood improves cognitive ability after measuring the fish intake of over 100 mothers and the “Visual Recognition Memory,” or VRO, of their six-month-old offspring. VRO is based on infants’ ability to perceive “novelty,” and is correlated with future IQ.

While omega-3 fatty acids may be beneficial to fetuses, Oken incorporated the FDA’s mercury warnings into her recommendation that women eat light canned tuna and white-meat fish, which are low in mercury and high on brain-boosting fatty acids.

Oken—who is, ironically, allergic to shellfish—says that while she is not sure if pregnant women will react to her paper by eating more fish, “it’s probably prudent” for them to follow the FDA regulations concerning shark and swordfish.

Within the next year, individual states will propose specific recommendations about what kinds of seafood are safe for pregnant women to eat.

In recent months, other Harvard researchers have also weighed in on the risks and benefits of fish consumption for expectant mothers.

“First of all, if you’re not pregnant, mercury is not an issue for you...that hasn’t come across enough,” said Joshua T. Cohen ’86, a senior research associate at the Harvard Center for Risk Analysis, which recently did a study on food advisories. “There are people cutting out their fish consumption when it’s not a problem. The tricky question is for women who are or are going to be pregnant. The answer is that they should be eating fish, but eating fish that are low in mercury.”

“On the one hand, you can warn women about the risk of fish consumption, but the risk is that...women might be scared off by fish altogether,” Cohen said. “Even worse, all adults might be scared off.”

“My ultimate hope is that contamination of seafood becomes less of an issue, so women can eat as much fish as they want without worrying that the fish may be contaminated with mercury or other pollutants,” Oken said.

Still, Oken said her work is incomplete. Her paper states that it does not take into account, for example, the IQ of the mothers her group studied, and that her “results should be generalized with some caution” since most of those mothers were educated, white, and well-off.

“With all epidemiological studies, we don’t just like to look at one study, we like to look at evidence from multiple studies together,” she said.