Pregnant women who eat fish more than three times a week are more likely to have obese children, according to new research.
The study showed eating a lot of fish while expecting was associated with mothers giving birth to babies at increased risk of rapid growth in infancy and of childhood obesity.
Researchers say fish is a common source of human exposure to persistent organic pollutants, which may exert endocrine-disrupting properties and contribute to the development of obesity.
In 2014, the U.S Food and Drug Administration and the Environmental Protection Agency encouraged women who are pregnant, breastfeeding or likely to become pregnant to consume no more than three servings of fish per week to limit foetal exposure to methyl-mercury.
The researchers, whose findings were published online by the journal JAMA Paediatrics, said there is no clear answer regarding the optimal amount and type of fish to eat during pregnancy with regard to child growth and development.
They analysed data from more than 26,000 pregnant women and their children in European and U.S studies to examine associations with fish consumption and childhood growth plus obesity. Children were followed until the age of six.
The average amount of fish eaten during pregnancy varied between study areas and ranged from 0.5 times per week in Belgium to 4.45 times per week in Spain.
High fish intake was classed as eating fish more than three times per week, while low fish intake was once a week or less and moderate intake was greater than once but not more than three times per week.
Of the children, 8,215 (31 per cent) were rapid growers from birth to two years of age, while 4,987 (19.4 per cent) and 3,476 (15.2 per cent) children were overweight or obese at ages four and six, respectively.
Women who ate fish more than three times per week when they were pregnant gave birth to children with higher BMI values at two, four and six years of age compared with women who ate fish less.
High maternal fish intake during pregnancy was also associated with an increased risk of rapid growth from birth to two years of age and with an increased risk of being overweight or obesity for children at ages four and six compared with maternal fish intake while pregnant of once a week or less.
The researchers said the magnitude of the effect of eating fish was greater in girls than boys.
Doctor Leda Chatzi, of the University of Crete in Greece, said: “Contamination by environmental pollutants in fish could provide an explanation for the observed association between high fish intake in pregnancy and increased childhood adiposity.”
However, she said that while the researchers collected information on the consumption of different fish types, they did not have enough data to distinguish between species, cooking procedures or whether the fish was from rivers or the sea.
Dr Chatzi added: “In the absence of information regarding levels of persistent organic pollutants across participating cohorts, our hypothesis that fish-associated contaminant exposure may play a role in the observed associations remains speculative.
“Our findings are in line with the fish intake limit for pregnancy proposed by the US Food and Drug Administration and Environmental Protection Agency.”