Pregnant women have always done it. Eating fish while expecting has been considered healthy, universally.
Not any more, according to scientists from Taipei, Taiwan.
A study, to be published in the British Journal of Obstetrics and Gynecology; January 2007, was conducted on pregnant women into their 24 Th week. Amounts of mercury in the umbilical cord, placenta as well as the blood of the fetuses were noted to be way ahead of the optimum levels. In the umbilical cord a mercury level of 10 microgram per liter was noted and a measure of 19 micrograms per liter in the placenta.
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 per liter.
Researchers noted that Taiwanese women tend to eat more fish during pregnancy, believing that it is a more nutritious source of protein than red or white meat.
When a woman consumes fish, it is absorbed in the gastrointestinal tract and enters the bloodstream. The trace elements of mercury, or methyl mercury, the commonly found form of mercury in fish, pass through the placenta and then to the fetus.
Elevated mercury levels have been linked to learning disabilities and developmental delays in children. There is also the danger of damage to the heart, nervous system and kidney. Fetuses exposed to higher mercury levels could also risk improper organ development.
Phil Steer, editor of the journal said the research 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.''
The US Food and Drug Administration advises 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.