Regression analyses using the self-report measures of alcohol consumption revealed paradoxical findings in that alcohol was found to have a beneficial effect on balance ability, for several measures of exposure and for several of the balance outcomes. Such apparently beneficial effects of prenatal alcohol have been previously reported in different neurodevelopmental contexts, eg. Kelly et al, 2009.
Given the biological implausibility of this outcome, a final set of analyses were completed using the ADH1B gene as an instrumental variable to “deconfound” the analyses. No associations were found between ADH1B genotype and the balance outcome measures. Drinking alcohol during pregnancy was therefore not found to affect balance in children. The apparent beneficial effects of prenatal alcohol exposure found when using the self-report measures of alcohol consumption were in fact the result of residual confounding.
IMPLICATIONS
The results of this study indicate that maternal alcohol consumption in pregnancy at “real-life” levels does not affect balance in children of ages 7 and 10 years. Although initial analyses based on self-report measures of alcohol consumption suggested a beneficial effect of alcohol, instrumental variable analyses showed that these beneficial effects were in fact a result of residual confounding. Other researchers in this field need to be aware of the possibility of residual confounding and that the ADH1B gene can be used to “deconfound” analyses.
Further research in this area is needed, particularly using measures of alcohol consumption during the pre-pregnancy recognition period and using alternative measures of childhood balance.