More Evidence Light Drinking During Pregnancy May Not Be Harmful to Offspring

Experts Say This Should Not Be Interpreted as a Green Light for Drinking While Pregnant

Megan Brooks

October 19, 2010

October 19, 2010 — A new study from Western Australia has found no link between low and moderate alcohol consumption during pregnancy and alcohol-related birth defects. There was, however, a significantly increased risk for birth defects with heavy prenatal alcohol exposure, as expected.

The new study, published in the October issue of Pediatrics, echoes findings from a British study, which generated considerable media attention in recent weeks. The British study, published October 5 in the Journal of Epidemiology and Community Health, found that light or moderate alcohol intake during pregnancy did not increase the risk for clinically relevant behavioral or cognitive problems in infants at 5 years of age.

On the heels of both of these studies, several professional groups have weighed in, including the International Scientific Forum on Alcohol Research, a joint undertaking of the Institute on Lifestyle & Health of Boston University School of Medicine in Massachusetts and Alcohol in Moderation (AIM) of the United Kingdom. Forum members are not paid; members are researchers who share their knowledge and expertise and put recent research into context with other studies.

Strong Reaction

Publication of these studies has fueled strong reaction, R. Curtis Ellison, MD, codirector of the forum and professor of medicine and public health at Boston University, told Medscape Medical News. "I have just finished responding to an irate person who evidently treats women alcoholics in Australia, and the last thing she wanted to hear was a message other than just say no to alcohol," he added.

While no one is advocating that pregnant women drink alcohol, we believe it is important that we use evidence-based data when making guidelines for alcohol consumption during pregnancy, and these [2 new studies] add to that database.

"While no one is advocating that pregnant women drink alcohol, we believe that it is important that we use evidence-based data when making guidelines for alcohol consumption during pregnancy, and these [2 new studies] add to that database," noted Dr. Ellison.

"We conclude that while drinking during pregnancy should not be encouraged, there is little evidence to suggest that an occasional drink by the mother is associated with harm," according to a forum statement issued late last week.

"It is estimated that 20% of women do not realize they are pregnant during the first 3 weeks of gestation, so unneeded worry if mums-to-be have been drinking lightly is really the key,” Helena Conibear, codirector of the forum and executive director of AIM, told Medscape Medical News.

Giovannie de Gaetano, MD, PhD, of the John Paul II Center for High Technology Research and Education in Biomedical Sciences, Catholic University, Rome, Italy, agreed. "At the moment, we should not encourage pregnant women to drink, obviously, without terrorizing those pregnant women who are occasional or light drinkers."

In the Australian study, Colleen M. O'Leary, MPH, PhD, of Telethon Institute for Child Health Research, University of Western Australia in Perth, and colleagues examined associations among dose, pattern, and timing of prenatal alcohol exposure and birth defects.

The investigators linked data from a randomly selected, population-based cohort of 4714 nonindigenous women who gave birth to a live infant in Western Australia between 1995 and 1997 to birth defects registry data from Western Australia. Information about maternal alcohol consumption was collected 3 months after birth for the 3-month period before pregnancy and for each trimester separately.

The Australian Study

A standard drink in Australia contains 10 grams of alcohol. Low alcohol consumption was defined as fewer than 7 standard drinks per week and no more than 2 drinks on any given day, in line with recommendations set out by the Australian National Health and Medical Research Council in 2001.

The moderate drinking category included women who consumed 7 drinks or less per week, with most consuming roughly 2 to 5 drinks per occasion; therefore, the quantity consumed per occasion discriminated moderate consumers from low consumers, the researchers explain in their report. Heavy drinking was defined as more than 7 drinks per week.

In the first trimester, 40.8% of women abstained from alcohol, 28.1% were low alcohol consumers, 10.8% were moderate drinkers, and 3.7% were heavy drinkers. In late pregnancy, these percentages were 40.8%, 38.1%, 10.8%, and 2.2%, respectively.

The study authors note that although a large proportion of women in this cohort drank alcohol while pregnant, the prevalence of any birth defect classified as alcohol related by the Institute of Medicine was "low." A total of 306 children (6.5%) were diagnosed as having any birth defect, whereas only 51 (1.1%) had birth defects deemed alcohol related.

"An interesting aspect of this study was that a large proportion of the alcohol-related birth defects (ARBDs) found in the children were unrelated to alcohol exposure so were in all probability misclassified as being alcohol related," said Dr. Ellison.

In the study, there was no association between low or moderate prenatal alcohol exposure before or during pregnancy and the occurrence of any birth defect or birth defects classified as alcohol related.

Heavy drinking in the first trimester (compared with abstinence) was associated with greater than 4-fold increased odds of birth defects classified as ARBDs. The adjusted odds ratio was 4.57 (95% confidence interval, 1.46 – 14.26). Nearly two-thirds (62.7%) of the birth defects classified as ARBDs were ventricular septal defects, and 15.7% were atrial septal defects.

"Our findings are consistent with the fact that the first trimester is a period of rapid fetal development and the most vulnerable time for the occurrence of structural birth defects," Dr. O'Leary and colleagues write.

They also note that birth defects defined as ARBDs occurred in each drinking category, with 47% occurring in infants born to women who did not drink during the first trimester.

"This indicates the difficulty in reliably attributing these birth defects to alcohol in clinical settings, particularly because the dose, pattern, and timing of prenatal alcohol exposure are not recorded routinely."

The British Study — A Recap

In the previously reported British study involving more than 11,000 children, those 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. Actually, these problems were less common among children exposed to “light” amounts of alcohol before birth.

Once again, heavy drinking while pregnant was clearly harmful, the study authors found.

In this study, 1 drink was defined as 1 glass of wine, a half pint of beer, or a single measure (25 mL) of spirit or liqueur.

Dr. Ellison noted that these and other recent studies on light drinking in pregnancy indicate that socioeconomic, education, and other lifestyle factors of the mother may have large effects on the health of the fetus, and these need to be considered when evaluating the potential effects of alcohol during pregnancy.

"It has been well demonstrated in numerous studies," Dr. Ellison noted, "that women with less education, lower income, less access to prenatal care, etc, are at higher risk of having children with abnormalities even though they may report only light if any alcohol intake during pregnancy. A number of lifestyle factors, including smoking, drug usage, binge drinking, underreporting of alcohol use, are thought to contribute to their higher risk.

"Studies suggest that women with higher education, income, and other measures of socioeconomic status are much less likely to have infants with abnormalities, and current data do not suggest that light alcohol intake among such women in an important factor in leading to birth defects in their children," Dr. Ellison added.

The Bottom Line

Summing up, he said, the Australian and British studies join "a number of other recent studies that have not shown abnormalities in newborns or in older children that relate to occasional or light drinking by the mother during pregnancy. We realize that residual confounding is always a possibility in observational studies, and there is no way that a randomized controlled trial can be done to deal with these questions. Hence, we are forced to use our best judgment in reaching conclusions."

We realize that residual confounding is always a possibility in observational studies, and there is no way that a randomized controlled trial can be done to deal with these questions. Hence, we are forced to use our best judgment in reaching conclusions.

Currently, most countries, including the United States, Canada, France, and Italy, recommend that women planning to conceive or who are pregnant abstain from drinking alcohol.

In the United Kingdom, the National Institute for Health and Clinical Excellence (NICE) currently recommends that women avoid alcohol during the first trimester because it may be associated with an increased risk for miscarriage.

Women who choose to drink alcohol during pregnancy are advised to drink no more than 1 to 2 UK units of alcohol once or twice a week. "Although there is uncertainty regarding a safe level of alcohol consumption in pregnancy, at this low level there is no evidence of harm to the unborn baby," the guidelines state. The Royal College of Obstetricians and Gynaecologists' stance echoes the NICE guidance.

In the United States, the American College of Obstetricians and Gynecologists (ACOG) told Medscape Medical News it continues with its long-standing position that no amount of alcohol consumption can be considered safe during pregnancy. The bottom line, according to an ACOG statement, is "women should avoid alcohol entirely while pregnant or trying to conceive."

None of the researchers has disclosed any relevant financial relationships.

Pediatrics. 2010;126:e843-e850.


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