Heavy Prenatal Alcohol Exposure Disrupts Brain Development

Deborah Brauser

November 02, 2012

Heavy prenatal exposure to alcohol may disrupt proper brain development during childhood and adolescence, new research suggests.

An international, multisite study of 133 children and youth showed, through the use of structural magnetic resonance imaging (MRI) scans, that those who had mothers who drank heavily during pregnancy had significantly decreased brain plasticity compared with the children whose mothers did not drink.

Brain plasticity is important for learning new skills and for adapting to various environments throughout life.

In addition, the participants who had heavy alcohol exposure showed lower scores on tests of intelligence and more severe facial abnormalities.

"I think this study is important because it shows that brain development can be altered over time by alcohol exposure that occurs in utero," coinvestigator Elizabeth R. Sowell, PhD, director of the Developmental Cognitive Neuroimaging Laboratory at Children's Hospital Los Angeles and professor of pediatrics at the University of Southern California, told Medscape Medical News.

Dr. Elizabeth Sowell

"The main message is that this is totally preventable. We don't know how much alcohol is enough to cause brain damage. So if you're pregnant or trying to get pregnant, it's best to avoid alcohol," added Dr. Sowell.

She noted that this is one of the first long-term, longitudinal studies to look at this topic.

"Our observations also indicate that after exposure, these brain abnormalities are not static. It may be possible to correct developmental trajectories," she said.

"Intervention could be key to helping these kids. It's too late to take back their early exposure to alcohol, but it may not be too late to alter the environment in some way to impact that malleable brain change for the better."

The study is published in the October 31 issue of the Journal of Neuroscience.

Static Growth

According to the researchers, normal brain development shows rapid brain volume increases at a young age, followed by decreases in certain regions during adolescence.

For this study, 70 children and adolescents between the ages of 5 and 15 years (mean age, 12.4 years) with heavy prenatal alcohol exposure and 63 age-matched healthy peers were enrolled at 3 sites: Los Angeles, California; San Diego, California; and Cape Town, South Africa.

All participants underwent 2 MRI scans to measure changes in cortical volume. The second scan was performed approximately 2 years after the first one.

Heavy prenatal alcohol exposure was defined as more than 4 drinks per occasion at least once per week or more than 13 drinks per week during pregnancy.

Cognitive assessments were conducted using the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV). A trained dysmorphologist also examined most of the participants for abnormal facial features associated with fetal alcohol syndrome.

Results showed that the participants who were unexposed to prenatal drinking had a pattern of robust growth and typical reductions in the cerebral cortex. However, those who were exposed to prenatal drinking showed only cortical volume loss, with very little change between the scans.

"The pattern of static growth [in these children] was most evident in the rear portions of the brain — particularly the parietal cortex, which is thought to be involved in selective attention and producing planned movement," report the researchers in a release.

The exposed children also showed significantly greater facial dysmorphology than the unexposed children. This included shorter palpebral fissure length (P < .001) and higher upper lip ranks (P < .001) and philtrum ranks (P = .001).

They also had significantly lower full IQ scores on the WISC-IV (P = .02).

"This demonstrates that measures of IQ and facial dysmorphology predict, to some degree, the structural brain development that occurs in subsequent years," write the investigators.

In further analysis, of the 37 children with heavy prenatal alcohol exposure who were assessed for fetal alcohol spectrum disorder, 23 were found to have the disorder.

The study authors note that environment may have also played a significant role in the abnormal development of some of the participants.

"The differences in brain maturation may also be related to prolonged dysfunctional experiences throughout childhood and adolescence," said Dr. Sowell.

Clinical Implications

Still, this study "underscores that heavy drinking during pregnancy often has lasting consequences for the child's growth and development, and reminds us that women who are, who may be, or who are trying to become pregnant should not drink alcohol," said Ken R. Warren, PhD, acting director of the National Institute on Alcohol and Alcoholism (NIAAA), in a release.

The NIAAA provided major funding for this study.

Dr. Sowell noted that the findings may have implications for developing early interventions that could correct or at least improve these abnormal brain development patterns.

She added that the study might also help in the treatment of other brain development disorders, such as autism.

"We know that early intervention in kids with neurodevelopmental disorders is a good thing. And I think our longitudinal data are really pointing in the direction of explaining why early intervention works. It's because it impacts the way the brain is wired within the environment," said Dr. Sowell.

"It's never too late to try to intervene and make things better for these kids, whether it's through educational or behavioral interventions."

The study was supported by grants from the NIAAA, the National Institute on Drug Abuse, the National Institute of Child Health and Human Development, and the March of Dimes. The study authors have disclosed no relevant financial relationships.

J Neurosci. 2012;32:15243-15251. Abstract

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