Fetal Alcohol Spectrum Disorder
Light Drinking During Pregnancy Not Harmful to Offspring?
October 7, 2010 — Children born to women who drank 1 or 2 alcoholic beverages a week during pregnancy were not at increased risk for clinically relevant behavioral or cognitive problems at 5 years of age, a new study shows. However, investigators and at least 1 independent expert say these findings should be interpreted with caution.
In fact, "children born to light drinkers seemed to have fewer behavioral problems and higher cognitive scores than those born to moms who didn't drink during pregnancy," study investigator Yvonne Kelly, PhD, from the Department of Epidemiology and Public Health, University College London, United Kingdom, told Medscape Medical News.
A previous study of 3-year-old children, by the same researchers, yielded similar conclusions. "We looked at the same children again because of the possibility of 'delayed sleeper effects' (i.e., if light drinking were related to difficulties or deficits in children then these would likely to be emergent at 5 years of age)," Dr. Kelly explained.
The study was published online October 5 in the Journal of Epidemiology and Community Health.
Reached for outside comment, Marc C. Lewis, MD, service chief for Women's Health Services at Henry Ford Hospital in Detroit, Michigan, said the study is "interesting, but certainly warrants much more long-term data."
Although the short-term data suggest no increased risk for poor socioeconomic or cognitive developmental outcomes in children born to mothers who drank not more than 1 to 2 units of alcohol per week, "I agree with the authors' statement that further work to tease out etiological relationships is needed," Dr. Lewis told Medscape Medical News.
"We know that in the United States, the leading cause of mental retardation is related to fetal alcohol syndrome," he added, "and although the study was for light drinkers, I do not believe we want to establish a precedent that any level of alcohol consumption is okay, because in truth, we really don't know the long-term effects of even light drinking."
Most Women Did Not Drink While Pregnant
Dr. Kelly and colleagues used data from the Millennium Cohort Study, a large study that followed the health of a nationally representative sample of 11,513 children born in the United Kingdom between September 2000 and January 2002.
The children were grouped according to mothers' reported alcohol consumption: teetotaler; those who drank but not during pregnancy; light drinker (1 or 2 units a week or at any one time); moderate drinker (3 to 6 units a week or 3 to 5 at any one time); and binge/heavy drinker (7 or more units a week or 6 at a single sitting).
A unit was defined as 1 glass of wine, a half pint of beer, or a single measure of spirit or liqueur. "Without knowing whether the alcohol content of 1 or 2 units of a beverage are comparable in the United Kingdom and the United States, it is hard to gauge a direct correlation to the consumption of an equivalent amount in the United States," Dr. Lewis explained.
According to the investigators, 5.9% of mothers said they never drank alcohol, 60.2% said they did not drink during pregnancy, and 25.9%, 5.5%, and 2.5% were categorized as light, moderate, and heavy/binge drinkers, respectively.
The mothers provided information about their child's behavior at age 3. At age 5, the child's behavior and intellectual development was assessed using the Strengths and Difficulties Questionnaire and British Ability Scales.
Across the entire cohort, boys were more likely than girls to have high scores on total difficulties (9.3% vs 6.0%), conduct problems (11.2% vs 7.9%), hyperactivity (12.8% vs 7.1%), and peer problems (7.3% vs 5.1%). Girls were more apt to have high emotional symptom scores than boys (9.5% vs 8.7%). Girls also had higher average cognitive ability test scores than boys, measured with a vocabulary test, picture similarities test, and pattern construction.
Boys and girls born to women who drank lightly during pregnancy were about 30% less likely to have behavioral problems than those born to women who did not drink during pregnancy, the authors found.
High scores for total difficulties were seen in 6.6% of boys of light drinkers and in 9.6% of boys of nondrinkers (odds ratio [OR], 0.67). For girls, these percentages were 4.3% and 6.2%, respectively (OR, 0.69). High hyperactive scores were seen in 10.1% of boys of light drinkers and in 13.4% of boys of nondrinkers (OR, 0.73); for girls, these percentages were 5.5% and 7.6% (OR, 0.71).
These differences were attenuated somewhat after adjustment for confounding and mediating factors, the authors note.
Cognitive tests also suggested no behavioral or cognitive harm from light drinking during pregnancy. Boys born to light drinkers had higher mean cognitive test scores than those born to mothers who did not drink; scores for naming vocabulary were 57.5 vs 55.1 words, respectively; for picture similarities were 56.3 vs 54.6; and for and pattern construction were 51.6 vs 50.0. The differences for naming vocabulary and picture similarities remained statistically significant in fully adjusted models.
Girls born to light drinkers, compared with those born to women who didn't drink, had higher mean scores on the naming vocabulary (57.6 vs 56.0) and pattern construction (53.0 vs 51.7) subscales, but differences were attenuated in the fully adjusted model.
This study, Dr. Kelly told Medscape Medical News, suggests that, for mothers who chose to drink lightly — no more than 2 drinks per week — "there appears to be no increased risk of behavioral or intellectual problems in their children [at age 5]."
Dr. Kelly and colleagues point to the observational nature of their study and caution that "causal inference based on observational data is limited."
They also note that data on mothers drinking during pregnancy were collected when the children were 9 months old, and although some studies report that retrospective recall of alcohol consumption is reliable, it is possible that the measure used in this study was prone to recall bias."
The study team further point outs that when not pregnant, 94% of the women said they drank alcohol, but only about 34% of mothers reported drinking during pregnancy; it is unclear what proportion of women stopped drinking before conception or before the pregnancy was recognized. "We also did not have data on trimester of drinking," Dr. Kelly noted.
A strength of the study, she added, lies in the way the women were segregated. "We disaggregated the nondrinking mothers into 2 groups — those who never ever drank and those who did not drink during pregnancy but otherwise were drinkers."
"For the purposes of statistical analysis, the latter group was used for comparison with light drinkers. This was a more robust approach than simply using all nondrinkers as the comparison group," she explained.
The analysis was supported by a grant from the Economic and Social Research Council. The study authors and Dr. Lewis have disclosed no relevant financial relationships.
J Epidemiol Community Health. Published online October 5, 2010. Abstract
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