Although deficits in measures of intelligence are well documented among children exposed to high amounts of alcohol during pregnancy, deficits among children prenatally exposed to low-to-moderate amounts of alcohol are much less understood. A study in the June issue of Alcoholism: Clinical & Experimental Research has found that even light to moderate drinking – especially during the second trimester – is associated with lower IQs in offspring at 10 years of age.
"The impact of heavy prenatal alcohol exposure on IQ ranges from a two- to a seven-point decrease," said Jennifer A. Willford, assistant professor of psychiatry at the University of Pittsburgh School of Medicine and lead author of the study. "IQ is a measure of the child's ability to learn and to survive in his or her environment. It predicts the potential for success in school and in everyday life. Although a small but significant percentage of children are diagnosed with Fetal Alcohol Syndrome (FAS) each year, many more children are exposed to alcohol during pregnancy who do not meet criteria for FAS yet experience deficits in growth and cognitive function."
"Intellectual functioning is a good first measure of the potential damaging effects of prenatal alcohol exposure," added Paul D. Connor, clinical director of the Fetal Alcohol and Drug Unit and assistant professor in the department of psychiatry and behavioral sciences at the University of Washington. "However, mental retardation only characterizes a minority of patients with FAS and Alcohol-Related Neurodevelopmental Disorder (ARND). There are a number of domains of cognitive functioning that can be impaired even in the face of a relatively normal IQ, including academic achievement (especially arithmetic), adaptive functioning, and executive functions (the ability to problem solve and learn from experiences). Deficits in intellectual, achievement, adaptive, and executive functioning could make it difficult to appropriately manage finances, function independently without assistance, and understand the consequences of – or react appropriately to – mistakes."
Willford analyzed data collected as part of the Maternal Health Practices and Child Development Project, an examination of prenatal substance use among women who attended a prenatal clinic from 1983 to 1985. Women were assessed during each trimester of pregnancy, and again with their children at birth, eight and 18 months, and three, six and 10 years of age. This particular study examines 611 mother-child pairs, which represents 80 percent of the birth sample. At age 10, the children's cognitive ability was assessed using the composite score and verbal, abstract/visual, quantitative, and short-term memory area scores of the Stanford Binet Intelligence Test - Fourth Edition.
"This study found that even light to moderate drinking during pregnancy can affect IQ," said Willford. "The effects of prenatal alcohol exposure on IQ were worse for children exposed to alcohol through the second trimester of pregnancy."
"This latter finding," said Connor, "of greatest effects on intellectual functioning because of second-trimester drinking suggests that, with appropriate intervention procedures, even if alcohol was consumed early during pregnancy, cessation of drinking as soon as possible could have protective benefits on the developing fetus. This is one of the few longitudinal studies of prenatal alcohol exposure that specifically collected data on the timing of alcohol use and is a strength of the study."
"Our study also showed that prenatal alcohol exposure was associated with lower IQ for African-American but not Caucasian children, said Willford. "Importantly, we know that this racial difference was not due to differences in the amount or pattern of alcohol use during pregnancy or by differences in socioeconomic status. We cannot say why the racial difference exists, but laboratory animal and human studies show that it may be partly explained by genetic factors."
"Similar findings have been described in other studies," concurred Connor, "however, it should not be construed that a child is protected from the damaging effects of prenatal alcohol exposure because of their ethnicity. Fetal Alcohol Spectrum Disorders can occur in any ethnic group."
Both Willford and Connor emphasized that it remains unclear if there is a "safe" level of alcohol consumption during pregnancy.
"The Surgeon General's recommendations in 1981 and 2005 that 'women who are pregnant or considering pregnancy should refrain from consuming alcohol' are extremely important," said Connor. "Routine queries by medical professionals about a woman of child-bearing age's drinking patterns are a vital step for assisting in the prevention of damage due to prenatal alcohol exposure. The best policy is to refrain from alcohol consumption during pregnancy or when planning to become pregnant, or if drinking occurs after conception, to cease drinking as soon as possible after learning of a pregnancy."
Alcoholism: Clinical & Experimental Research (ACER) is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. Co-authors of the study, "Moderate Prenatal Alcohol Exposure and Cognitive Status of Children at Age 10," were S.L. Leech and N.L. Day of the Department of Psychiatry at the University of Pittsburgh School of Medicine. Funding for the study was provided by the National Institute on Alcohol Abuse and Alcoholism.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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