Hibbeln JR, Davis JM, Steer C, Emmett P, Rovers I, Williams C, Golding J. (2007) The Lancet 369 578-85
Web URL: View Full Abstract via PubMed
Seafood is the predominant source of omega-3 fatty acids, which are essential for optimum neural development. However, in the USA, women are advised to limit their seafood intake during pregnancy to 340 g per week.
We used the Avon Longitudinal Study of Parents and Children (ALSPAC) to assess the possible benefits and hazards to a child's development of different levels of maternal seafood intake during pregnancy.
11,875 pregnant women completed a food frequency questionnaire assessing seafood consumption at 32 weeks' gestation. Multivariable logistic regression models including 28 potential confounders assessing social disadvantage, perinatal, and dietary items were used to compare developmental, behavioural, and cognitive outcomes of the children from age 6 months to 8 years in women consuming none, some (1-340 g per week), and >340 g per week.
After adjustment, maternal seafood intake during pregnancy of less than 340 g per week was associated with increased risk of their children being in the lowest quartile for verbal intelligence quotient (IQ) (no seafood consumption, odds ratio (OR) 1.48, 95% CI 1.16-1.90; some, 1.09, 0.92-1.29; overall trend, p=0.004), compared with mothers who consumed more than 340 g per week.
Low maternal seafood intake was also associated with increased risk of suboptimum outcomes for prosocial behaviour, fine motor, communication, and social development scores. For each outcome measure, the lower the intake of seafood during pregnancy, the higher the risk of suboptimum developmental outcome.
Maternal seafood consumption of less than 340 g per week in pregnancy did not protect children from adverse outcomes; rather, we recorded beneficial effects on child development with maternal seafood intakes of more than 340 g per week, suggesting that advice to limit seafood consumption could actually be detrimental.
These results show that risks from the loss of nutrients were greater than the risks of harm from exposure to trace contaminants in 340 g seafood eaten weekly.
This research used data from the large ALSPAC (‘Children of the 90s’) to assess a range of developmental outcomes in children according to their mother’s intake of fish and seafood during pregnancy, controlling for a very wide range of other factors already known to affect these outcomes.
Children of mothers whose fish and seafood intake during pregnancy was within current guidelines (the US recommends a maximum of 340g, similar to the UK guidance to limit intake to two portions a week, one of which should be oily fish) had poorer neurodevelopmental outcomes than those whose mothers exceeded this intake.
And the worst neurodevelopmental outcomes - i.e. the highest risks for suboptimal verbal intelligence, motor skills, social skills and other outcomes - were seen in the children whose mothers ate no fish or seafood during their pregnancy.
See the Times article, citing the authors' views on this subject: Fish-Diet Mothers have brighter children
Randomised controlled treatment trials offer the only *definitive* way to confirm cause-and-effect relationships, but such trials are obviously impossible to conduct when it comes to important questions like the link between fish-eating during pregnancy and children's brain development.
These findings cast serious doubt on the wisdom of current dietary advice to pregnant women, and suggest that it may in fact be doing harm.
An urgent review of the dietary guidance concerning fish and seafood consuption during pregnancy is now clearly warranted - along with further investigations - as a matter of urgency.