Pregnant women who have a fish intake of above three times in a week have a possibility of putting their baby at risk, thanks to the higher mercury levels in their blood, states a study by Taiwan researchers.
Mercury exposure poses a great risk to fetuses when their internal organs are developing, and can result in neuronal, kidney and brain damage, and stunt growth.
Expectant Chinese mothers tend to eat more fish as they believe it is healthier than red or white meat.
A study of 65 pregnant women in Taipei revealed that mercury concentrations of around 9.1 micrograms per liter in their blood and around 10 micrograms per liter in blood in their umbilical cords. The researchers also found an average of 19 nanograms per gram of mercury in their placenta.
Such levels are much higher that what are considered safe, the researchers wrote in a paper to be published in January 2007 in the International Journal of Obstetrics and Gynecology.
Phil Steer, editor of the journal said the research further demonstrates “how food eaten by a pregnant mother affects the child in her womb… The message to take home from this is not ‘Stop eating fish’ but ‘Be careful which fish you eat, and how often.'”
Eighty-nine percent had blood mercury concentrations exceeding the US National Research Council’s recommended value of 5.8 micrograms per liter.
The women were recruited for the study 24 weeks into their pregnancy.
Researchers said, “When a woman consumes fish, it is absorbed in the gastrointestinal tract and enters the bloodstream. The trace elements of mercury, or methylmercury, the commonly found form of mercury in fish; passes through the placenta and then to the fetus.”
The US Food and Drug Administration recommends pregnant women to avoid eating fish with high mercury levels such as shark, swordfish, king mackerel and tilefish.
Instead, it recommends fish and shellfish that are lower in mercury, such as shrimp and tilapia.
The U.S. National Research Council (USNRC) and U.S. Environmental Protection Agency (USEPA) recommend that mercury levels in cord blood should not exceed 5.8 microgram/l.