Once upon an innocent time, we all thought that a diet rich in fish was good for us. Then we found out that, just as land-based foods are contaminated with pesticides, the fish were full of mercury.
It's a worry for all of us, and especially for the expectant mother. Will her fish-rich diet affect the development of her unborn child?
According to researchers at the National Institutes of Health, mercury - certainly the type from fish - doesn't cross the placenta.
They tested the neurocognitive, language, memory, motor and behavioural skills of 779 infants born to women in the Seychelles who eat on average 12 fish meals a week.
The fish in the oceans around the Seychelles have similar mercury levels to those fished in other parts of the world, the researchers say. This was confirmed when they analysed the mothers' hair, which had mercury levels of 6.9 parts per million.
The children were tested on a number of times during their developing years up until the age of 9, and the researchers were able to detect any problems at any of the stages.
Of course, add the researchers, this cannot provide definitive proof. The women of the Seychelles eat a wide variety of fish, and their diets may have a positive impact on the effects of mercury.
Still, it does offer genuine hope to any mother who might have been concerned. Now all she has to do is have her amalgam fillings removed.
(Source: The Lancet, 2003; 361: 1686-92).