There is little question that women who drink heavily during pregnancy place their children at risk of developing fetal alcohol syndrome (FAS), characterized by growth retardation, craniofacial anomalies, and mental retardation. However, women who drink moderate amounts of alcohol may also place their children at risk of developing less severe deficits (once known as fetal alcohol effects but now called alcohol-related neurodevelopmental disorder), characterized by a lower IQ, attention deficits, learning deficits, and reduced social competence. A study in the August issue of Alcoholism: Clinical & Experimental Research has discovered that a crucial factor for the developing fetus may be when a woman drinks. Researchers found that moderate alcohol exposure during early pregnancy may be just as damaging to neurobehavioral development as continuous or late exposure.
"Previous research has found that alcohol exposure later in pregnancy is strongly associated with problems in growth and behavioral development," said Mary L. Schneider, professor of occupational therapy and psychology at the University of Wisconsin-Madison and lead author of the study. "Yet women who report drinking late in pregnancy have usually consumed alcohol throughout and so it is hard to disentangle early drinking from late drinking. In addition, while animal studies have established that high doses cause numerous impairments, many questions remain regarding the issue of moderate fetal alcohol exposure. Since many women of childbearing age drink alcohol regularly, it is likely that some offspring are exposed to alcohol before pregnancy is detected. These are just some of the reasons for why I felt it was important to examine the effects of moderate drinking at different times during pregnancy."
Study subjects were rhesus monkey infants whose mothers consumed a moderate dose of alcohol either continuously or during the human equivalent of the first or last two trimesters of pregnancy. (Moderate drinking in humans is defined as 7 to 14 drinks per week, or 1 to 2 drinks per day.) Schneider explained that not only do primate studies allow greater generalization to humans than rodent studies because of similarly complex social and cognitive abilities and brain development, but they are also less complex than "real life." Among humans, she said, alcohol consumption can be confounded with cigarette smoking, less-than-adequate prenatal care, stress, and other drug use – all of which can have negative effects on fetal development. In addition, researchers can use adapted human tests such as the Brazelton Newborn Assessment Scale to assess early neurobehavior in monkeys.
"We found that early gestation alcohol exposure was related to noteworthy reductions in infant attention and motor maturity in rhesus monkeys," said Schneider. "Yet there were no significant growth impairments. Thus, it appears that behavioral effects can be detected under circumstances in which growth was not affected. We also found that early exposure was as harmful as exposure throughout pregnancy in these monkeys. To the extent that these data generalize to humans, it suggests that subtle neurodevelopmental effects could be induced before pregnancy is detected."
"There are at least four very important aspects to this research," noted Joanne Weinberg, professor of anatomy at the University of British Columbia. "The primate model is very powerful in this case because it allows researchers to carry out sophisticated neurobehavioral tests, comparable to tests used in humans, to see what the effects of alcohol are. Another important aspect concerns the moderate levels of alcohol exposure. There are very few physical problems in these animals, you don’t see deficits in growth, and yet functionally they’re not normal. This finding probably has relevance for a more substantial percentage of the population. The third aspect is one of timing. I think it’s really critical to know when alcohol has its effects on fetal brain development because this gives us clues as to how and why these effects occur. Finally, the data from this study clearly separate early exposure from continuous exposure. This relates back to the advantages of animal research, where you can target drinking to specific times during pregnancy instead of asking people to self report on their drinking behavior."
For Schneider, the study’s findings have a clear message. "Women of childbearing age should abstain from consuming alcohol if they are considering pregnancy," she said.
Weinberg concurs. "We need to see more education for both the general public and physicians about the fact that alcohol can be harmful," she said, "and that we really don’t know what a safe level of drinking during pregnancy would be. Although the public is now more aware of FAS, they know much less about the more subtle effects that alcohol can have on a developing fetus. Even some pediatricians and obstetricians are not very well informed about the effects of moderate levels of fetal alcohol exposure, although they may know about FAS. The bottom-line message is that, ‘if you’re pregnant or thinking of becoming pregnant, we don’t know what a safe level for drinking is, and you’re better off not drinking at all.’"
Funding for this Addiction Science Made Easy project is provided by the Addiction Technology Transfer Center National Office, under the cooperative agreement from the Center for Substance Abuse Treatment of SAMHSA.
Articles were written based on the following published research:
Schneider, M.L., Moore, C.F., & Becker, E.F. (2001, August). Timing of moderate alcohol exposure during pregnancy and neonatal outcome in rhesus monkeys (Macaca Mulatta). Alcoholism: Clinical and Experimental Research, 25(8), 1238-1246.