Children who were exposed to alcohol in utero perform simple cognitive tests adequately, but fall short of their peers on more complex tasks, researchers say.

The study by Wayne State University researchers, who looked at the impact of moderate to heavy prenatal alcohol exposure, confirmed earlier studies that found slower processing speed and efficiency among alcohol-exposed children, especially on tasks involving working memory.

The alcohol-exposed kids especially struggled when they were asked to respond quickly to questions. “This suggests that processing speed deficits are more likely to occur within the context of some cognitive demand,” said Burden. “We also found that prenatal alcohol exposure was associated with poorer efficiency on number processing, a finding consistent with past research showing more specific adverse effects in the arithmetic domain. Arithmetic performance may be relatively more compromised with prenatal alcohol exposure than other types of intellectual performance, such as verbal abilities.

“We also looked at how processing speed related to other aspects of cognition, working memory in particular,” he added. “Prenatal alcohol exposure had some impact on both speed and working memory, but the effect on working memory was partly accounted for by the deficits in speed — in other words, slower performance contributes in part to poorer working memory.”

The authors said that the findings help illustrate why alcohol-exposed children have more problems later in their school careers. “Prenatal alcohol exposure is often associated with slower reaction times and poorer attention in infancy, and some of these deficits may be at the core of poorer academic performance and behavior problems often seen later in childhood,” said Matthew J. Burden, corresponding author for the study. “In cases of fetal alcohol syndrome (FAS) … lower IQ scores are common, often reaching the level of mental retardation. This is because alcohol consumed by the mother has a direct impact on the brain of the fetus.

“However, full FAS is not required to see this impact; it is just less obvious to detect across the array of exposures found in foetal alcohol spectrum disorders (FASD), which include effects of prenatal alcohol at lower drinking levels.”