Mamas on Bedrest: How Much Alcohol is Safe?

October 25th, 2010

Recently there has been a flurry of comments flying both in the news and the medical community. Two studies have published data stating that they found no link between low to moderate drinking during pregnancy and birth defects in infants and children.

The first study, Light Drinking During Pregnancy: Still No Increased Risk for Socioemotional Difficulties or Cognitive Deficits at 5 Years of Age? was published on October 5, 2010 in The Journal of Epidemiology and Community Health . British researchers found that by age 5 years,  study members born to mothers who drank up to 1–2 drinks per week or per occasion during pregnancy were not at increased risk of clinically relevant behavioral difficulties or cognitive deficits compared with children of mothers in the non-drinking group.

The debate got even more heated when a study out of Australia found similar results.  Colleen O’Leary, PhD, et. al.  set out to evaluate if there is an association between how much alcohol a pregnant woman drinks, when in her pregnancy she drinks and the development of birth defects in the child. O’Leary and her colleagues found that

“A fourfold increased risk of birth defects classified as Alcohol Related Birth Defects (ARBD’s) was observed after heavy Prenatal Alcohol Exposure (PAE) in the first trimester. Many individual birth defects included in the Institute of Medicine classification for ARBDs either were not present in this cohort or were not associated with PAE.”

Prenatal Alcohol Exposure and Risk of Birth Defects Pediatrics. 2010;126:e843-e850.

O’Leary and her colleagues went on to say that more large population studies are needed before any definitive conclusions or recommendations can be made.

Currently, the research conclusion is that since the evidence to date has shown that 1-2 drinks on occasion or weekly does not appear to be harmful to the fetus, infant or child,  there is no scientific justification to make the statement that alcohol consumption should be completely avoided during pregnancy. However, physicians and researchers who treat pregnant alcoholics and their neonates, infants and children suffering from the effects of prenatal alcohol exposure advocate for absolutely no alcohol consumption during pregnancy and have railed against the studies.  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. The American Congress of Obstetricians and Gynecologists (ACOG) continues with its long-standing position that no amount of alcohol consumption can be considered safe during pregnancy and they do not advocate alcohol consumption at all during pregnancy. They stand firm in their statement that,

“women should avoid alcohol entirely while pregnant or trying to conceive.”

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.

How is one to make any sense of all of the news reports and the scientific data? How are we to interpret what is being reported by researchers and sensationalized by the news media?

Dr. Ira Chasnoff* is one of the nation’s leading researchers in the field of maternal drug use during pregnancy and the effects on the newborn, infant and child. He has written an excellent editorial about these studies, the British study in particular. He examined how the studies were carried out, how the data has been interpreted and what his findings have been in his research on the effects of drugs and alcohol on a developing fetus. Here we present a summary of the major points in Dr. Chasnoff’s editorial, but you can read the full text here.

  1. Although the authors presented their findings in an evenhanded manner, the translation of the study findings in the national and international media has been anything but responsible. Headlines in newspapers and newscasts scream the message that light drinking of alcohol during pregnancy is not only perfectly safe, but actually results in higher developmental scores in children at five years of age. Such conclusions are not supported by the research and are reckless and misleading.
  2. Mothers were asked to recall their pattern of alcohol use during pregnancy nine months after having delivered. Multiple studies have shown that such recall is fraught with error when it comes to estimating the amount and frequency of alcohol use. The authors of the study recognized and stated that the study “was prone to recall bias.” (This is seldom if ever reported in media reports.)
  3. There is the significant demographic differences between the “light drinking” mothers and the other cohorts.
  4. Women who reported light drinking during pregnancy were less likely than any of the other groups to smoke suggesting the possibility that lack of prenatal or postnatal exposure to tobacco smoke might be a source for the differences seen between the children.
  5. Another limitation of the study is that the authors examined only the more global aspects of child development: behavioral and emotional functioning and cognitive ability.
  6. As the authors of the study pointed out, prenatal exposure to alcohol may have “sleeper” effects resulting in the emergence of developmental issues as children enter the school years. Because this study only evaluated children until age five, before they entered school, these potential developmental problems could not be captured. In this study the children have not yet been developmentally challenged in problem areas that typically begin to develop within a school environment, such as peer problems, hyperactivity and conduct.
  7. The methods of evaluation of the children are screening tools and not full assessment tools.
  8. Only 3 of a possible 14 assessments were carried out on the children. These specific three sub tests together have no validity for assessing overall cognitive functioning.
  9. While some reporters in the public media have presented thoughtful evaluations of the implications of the article in question, others have taken the information out of context and presented conclusions that the authors did not intend and that are not supported by the facts. In fact, the authors place a question mark at the end of their article’s title (Light drinking during pregnancy: still no increased risk for socioemotional difficulties
    or cognitive deficits at 5 years of age?
    ), indicating their inability to draw any firm and lasting conclusions about the effects of light drinking during pregnancy; instead, they state that “causal inference based on observational data is limited, and further work to tease out etiological relationships is needed.”

Which brings us to the public health response to the question,

“How much alcohol can a woman safely drink during pregnancy?” The answer is, “We don’t know.”

Multiple factors play into a child’s risk for developmental and behavioral difficulties, including genetics, the family environment in which the child is raised, and the intrauterine environment in which the fetus develops.

Importantly, we must realize that the U.S. population, with its wide range of races and ethnicities, is far more diverse than the all white population that was included in this study. The pregnant woman’s ability to metabolize alcohol varies greatly across race and ethnicity, so applying data developed on an all-white British population to the U.S. population with a broad mix of metabolic capabilities, is hazardous. Prenatal exposure to alcohol is known to impact the development of the fetal brain, and nothing in the recently published study from Great Britain concludes otherwise. Until we know more, we must advise people, in the best interest of unborn children, that no amount of alcohol is safe to drink during pregnancy.

*Ira Chasnoff, MD, serves as the president of the Children’s Research Triangle, a non-profit organization dedicated to the healthy development of children and their families. He is a Professor of Pediatrics at the University of Illinois College of Medicine in Chicago and is one of the nation’s leading researchers in the field of maternal drug use during pregnancy and the effects on the newborn infant and child. He is the author of The Mystery of Risk: Drugs, Alcohol, Pregnancy and the Vulnerable Child.

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