Mercury exposure from seafood during pregnancy may affect offspring growth

Low mercury exposure levels from moderate intake of seafood among moms appear to have a weak negative impact on child growth trajectories, a study has found.

The analysis included 51,952 mother-child pairs recruited in pregnancy and a subsample (n=2,277) with maternal mercury concentrations in whole blood. Individual growth trajectories were estimated by modelling based on child’s reported weight and length/height from 1 month to 8 years.

During pregnancy, the median maternal weekly intakes were 2.4 servings of total seafood, 1.3 servings of lean fish, and 0.6 servings of fatty fish. More than half of the women (66 percent) reported any intake of other seafood, with a weekly median of 0.3 servings. In total, 48 percent of the population ate 2–3 servings of total seafood and 13 percent >3 servings weekly during pregnancy.

Linear mixed-effects regression analysis showed that maternal lean fish was accounted for most of the total seafood intake in pregnancy and was positively but weakly associated with child body mass index (BMI) growth trajectory.

Meanwhile, higher prenatal mercury exposure correlated with a reduction in child’s weight growth trajectory, with the estimates ranging from –130 g at 18 months to –608 g at 8 years.

Maternal fatty fish consumption was positively linked to child weight and BMI growth trajectory, but only in the higher mercury-exposed children (p_interaction=0.045). Other seafood consumption during pregnancy was negatively associated with child weight growth relative to no intake, and this was evident among higher mercury-exposed children (p_interaction=0.004).

There was no association seen between discordant maternal seafood intake and child growth in the sibling analysis.

The present data on maternal seafood intake are likely noncausal, according to the researchers.