- Heavy drinking during pregnancy can cause major impairments in the developing child.
- New research indicates that light to moderate drinking may also interfere with learning and memory as late as adolescence, particularly in the auditory/verbal domain.
- Most of the drinking in this study occurred during the first trimester.
Many people know about the dangers of prenatal alcohol exposure, particularly the damaging effects that heavy drinking can cause to a child's cognitive development. A study published in the March issue of Alcoholism: Clinical & Experimental Research has found that even light to moderate drinking during pregnancy may interfere with learning and memory during adolescence.
"We have known for a long time that drinking heavily during pregnancy could lead to major impairments in growth, behavior, and cognitive function in children," said Jennifer Willford, assistant professor of psychiatry at the University of Pittsburgh School of Medicine, and the study's first author. "This paper clearly shows that even small amounts of alcohol during pregnancy can have a significant impact on child development."
"Learning and memory are cornerstones for success in school and in everyday life," added Sarah Mattson, assistant professor in the Department of Psychology, and associate director of the Center for Behavioral Teratology at San Diego State University. "Disruption of the ability to learn and remember new information jeopardizes the job of children, that is, to go to school. The inability to learn new information in the verbal or nonverbal domain will interfere with a child's ability to achieve alongside his or her peers."
The data examined in this study were collected as part of the Maternal Health Practices and Child Development Project (MHPCD), an ongoing longitudinal study of 580 children and their mothers. The MHPCD examines the effects of prenatal exposure to alcohol, marijuana, tobacco, and other illicit drugs on the growth, behavioral, and cognitive development of the offspring. Researchers measure demographic status, maternal psychosocial characteristics, household environment, and substance use at numerous intervals. They also assess the children's growth, and behavioral, neuropsychological, and academic status from birth onward.
For this study, mothers were assessed during each trimester of their pregnancies, and again with their children at regular intervals from birth to 16 years of age. Adolescent memory function was evaluated at 14 years of age (n=569) using the Children's Memory Scale, an assessment tool that measures learning and immediate and delayed memory function in the verbal and visual-spatial domains.
"We chose measures that would help us understand the types of learning and memory difficulties experienced by adolescents who were prenatally exposed to alcohol," explained Willford. "We assessed verbal/auditory and visual/spatial abilities because each of us learns through a combination of verbal and nonverbal abilities. We also examined learning and memory to determine whether subjects were having difficulty with initial learning, remembering information for a short time, or after a long period of time."
"During the first trimester," said Willford, "45 percent of the women drank, on average, less than one drink per day." Despite these relatively low levels of alcohol consumption, researchers found an association with subtle difficulties with learning and memory in the offspring at 14 years of age, specifically in the auditory/verbal domain. "This indicates that drinking during the first trimester of pregnancy … has long-term effects on development. Many women do not realize they are pregnant and/or seek prenatal care during this critical time," said Willford.
"These types of deficits have already been demonstrated in studies with much higher levels of exposure," added Mattson, "and thus, these data extend the continuum of effect to include lower levels of exposure. Another important finding is that the effects of alcohol exposure on memory for verbal information were mediated by verbal learning, a finding that has also been documented following higher levels of exposure. This finding is relatively novel in the field and thus the replication in a lower exposed sample suggests that this effect is specific to alcohol exposure."
Yet another finding concerns growth deficits among those children exposed to light to moderate drinking during gestation. "These findings parallel earlier reports of continued growth deficits among those children exposed to light to moderate drinking during their mothers' pregnancy," said Willford. "This shows us that prenatal alcohol exposure can lead to deficits in multiple domains."
Both Willford and Mattson said that findings such as these point out the potential dangers of drinking alcohol during pregnancy, and suggest that even lower than previously reported levels of alcohol consumption during pregnancy can have detrimental effects.
"There is no safe level of drinking during pregnancy and there is no safe time to drink during pregnancy," said Willford. "Women need this information before pregnancy recognition and their first visit to an obstetrician so that they may make better choices about drinking if they are planning to become, or think that they may be, pregnant."
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 ACER paper included: Gale A. Richardson and Nancy L. Day of the Department of Psychiatry at the University of Pittsburgh School of Medicine; and Sharon L. Leech of the University of Pittsburgh Medical Center. The study was funded by the National Institute on Alcohol Abuse and Alcoholism.