A new study of children in Bristol has shown that women who ate fish regularly during pregnancy had children with better language and communication skills by the age of 18 months.
In the USA, prospective mothers have been warned against eating more than 12 ounces of fish per week because of the effect of mercury poisoning on their unborn child.
But the researchers found that in the UK, where mercury levels in seafood are relatively low, the benefits of eating fish in moderation outweighed any risk from contamination.
Julie Daniels from the United States’ University of North Carolina at Chapel Hill analysed the diets of 7,400 mothers who are part of the Children of the 90s project, also known as the Avon Longitudinal Study of Parents and Children (ALSPAC) based at the University of Bristol. Her findings are published in the latest issue of the medical journal Epidemiology.
Ms Daniels says: “Fish is a source of many nutrients than can be beneficial during pregnancy, as well as a source of contaminants such as methyl mercury.
“Previous investigations of fish intake in relation to neurodevelopment have focused on possible damage from contaminants while the potential benefits have been relatively unexplored.”
The mothers were asked to record how often they ate fish, and what type, during pregnancy – and 70 per cent of women said they ate fish at least once a week.
The researchers studied the children’s cognitive development at 15 and 18 months, looking at standard tests of language, comprehension and social skills.
Overall – the study found that there was a subtle but consistent link between eating fish during pregnancy and children’s subsequent test scores, even after adjusting for factors such as the age and education of the mother, whether she breastfed, and the quality of the home environment.
The largest effect was seen in a test of the children’s understanding of words at the age of 15 months. Children whose mothers ate fish at least once a week scored 7 per cent higher than those whose mothers never ate fish.
The same pattern (although less marked) was seen in tests measuring social activity and language development. The developmental scores were also higher among children who also ate fish at least once a week before their first birthdays.
The scientists also examined the umbilical cords of 1,200 babies for presence of mercury. Overall levels were low, and while they found higher concentrations among women who ate fish, no link was found in the developmental tests.
The researchers noticed a threshold effect: while there was a benefit in eating fish in moderation – there was no advantage in eating large amounts of fish.
Ms Daniels reports: “The relationship with neuro-development was strongest for those eating fish between one and three times per week, with no additional benefit in eating fish more often.
“Fish consumption by pregnant women at this frequency (averaging 4 ounces per serving one to three times per week) is within the limit of 12 ounces of fish that are low in mercury advised by the US Food and Drug Administration and the US Environmental Protection Agency in March.”
“The balance between the benefits of fish and the adverse effects of mercury contamination in relation to neuro-development remain unclear for populations where mercury levels are higher.”
Fish intake during pregnancy in relation to offspring’s early cognitive development. Epidemiology. Daniels JL, Longnecker MP, Rowland AS, Golding J, ALSPAC Study Team.
Fish intake during pregnancy has the potential to improve foetal development because it is a good source of iron and long chain omega fatty acids, which are necessary for proper development and function of the nervous system. Fish, especially oily fish, is a dietary source of eicosapentaenoic and docosahexaenoic acids (DHA), which are important in the structural and functional development of the brain in utero and through the first year after birth. The concentration of DHA in foetal brain increases rapidly during the last three months in the womb.