Is Occasional Light Drinking During Pregnancy Harmful?

by Ernest L. Abel, Ph.D. and Robert J. Sokol, M.D.

In the last two decades more than 5,000 articles have been published on the effects of alcohol during pregnancy. One might assume we'd now have some consensus about the dangers of occasional light drinking during pregnancy. Unfortunately, this isn't so. Our own sober (no pun intended) conclusion, based on a critical evaluation of the literature, is that there are no known clinically important risks to the fetus from an occasional drink during pregnancy (see below for our definition of "occasional" and "light"). Here are our reasons.

1. Personal Experience

About two-thirds of all Americans drink to some extent. Our mothers and your mothers are probably among these 66%. One of us is a Dean of a Medical School (R.J.S.); the other is a Professor in Obstetrics and Gynecology (E.L.A.). While we are both hairless on top and somewhat funny-looking, we are both of normal size and stature, are both slightly pudgy, do not suffer from any visible birth defects, and though you may disagree with us, (for what are we arguing), we think we are of normal intelligence.

In other words, we don't look or act as if we have suffered as a result of our mothers' having had a drink or two during their pregnancies. We have also peered carefully at the minds and bodies of our children. While it's too soon to know for sure, none of them seems to be any more funny looking than we are, none of them seems to have suffered any loss of IQ points from the occasional drinks our spouses may have taken, and our food bills reflect their overwhelming commitment to eating.

Now it's your turn reader - do you or any of your children seem to have suffered as a result of an occasional motherly drink? Do you personally know of anyone that has?

2. Historical Evidence

When this country was on its way to nationhood, drinking was the norm. Our founding fathers and mothers drank far more than we do today. George Washington was a whiskey distiller, John Adams drank a tankard of hard cider every morning, Thomas Jefferson invented the presidential cocktail party. Historical information about drinking by women is hard to come by, but in the early 1800's there were an estimated "100,000 female drinkers" and many more "who consumed from one-eighth to one-quarter of the nation's spirituous liquor." We may be mistaken (because of the adverse effects of our own in-utero alcohol exposure), but we don't believe that the people who wrote our Constitution, Declaration of Independence, our Bill of Rights and the other laws by which we live, lost any IQ points by being exposed to more alcohol in-utero than we ourselves were. ( In raising this argument, we are more than aware of Dr. Johnson's percept concerning patriotism being the last refuge of the scoundrel).

3. Lies, Damned Lies, and Statistics

Lies. There is no practical objective way of knowing how much anyone drinks. We as researchers are therefore forced to rely on what people admit to when they are asked how many drinks they have a day, a week, a month, or something like this. But, how much is in a "drink?" We assume one drink is the same as another and each contains about 1/2 oz of alcohol. This just shows how naive we are. A bartender may use a "shot" glass but who else does? The amount of beverage actually consumed in a drink can vary from one to twelve ounces. If you pour most of your pint into a tall glass and I just pour a finger into mine, we'll both say we've had only one drink. If you were asking questions about income you wouldn't ask "how many times do you get paid a month?", would you? You'd want to know not only how often but how much someone gets paid. This would tell you a lot provided a dollar has the same value for everyone. But suppose you had Canadians and Americans in your study. Both might say they make $250 a week, but these dollars have different values in terms of what they will buy. Or suppose you asked Israelis and Britons how much they make. If both say they make 250 "pounds," do they make the same? Nuff said. You get the point.

Damned Lies. Simply asking someone who drinks a lot about how much he/she drinks is naive. People who drinks a lot don't like to admit it. They deny. Technically speaking, they lie. Sometimes they lie a lot. Trust a used car salesman before you trust what an alcoholic tells you about his or her drinking.

Self-reports of drinking during pregnancy are always suspect. Relating the dangers of a given number of "drinks" per day to a particular risk to the fetus based on this information is sophomoric. Because of denial, actual alcohol intake is underreported by the abusive drinker - the individual most likely to be at risk for giving birth to a child with alcohol related birth defects. The risk to the fetus of what might appear to be "2 drinks a day" is undoubtedly the result of a much higher intake.

Statistics. Alcohol is but one of many possible risk factors, such as social class, maternal illness, genetic susceptibility, smoking, diet, past health history, pregnancy complications, use of drugs and exposure to environmental pollutants. In epidemiology, statistical techniques are used to try to "even out" as many of these cofactors as possible. The goal is to match people as closely as possible except for their alcohol use. If you are going to do this carefully, you especially need to control for heredity. Charles Dickens made this point cogently in Pickwick Papers when he wrote about a meeting of "The Brick Lane Branch of the United Grand Junction Temperance Association." One of the new members was "Betsy Martin, widow, one child and one eye. Goes out charring and washing by day; never had more than one eye, but knows her mother drank bottled stout, and shouldn't wonder if that caused it."

Consider IQ scores. If you are studying the causes of subnormal IQ, isn't is reasonable to start with parental IQ? Claire Ernhart and her coworkers did this when they examined the effects of lead in children. They found lead was associated with decreased scores in cognitive and verbal tests but when parental IQ was incorporated into the analysis, the relationship was no longer significant. No studies in fetal alcohol research have bothered to include parental IQ as a factor. In a recent study, Ann Streissguth and her coworkers used parental education as a surrogate for IQ, the assumption being the more years in school, the higher the IQ. She then matched subjects on parental school years. Black children were included in the test but race could not be considered in the regression analysis because of the "relatively small number" of black children. If these were so few, why were they included at all? This point would be totally academic except for the fact that the only 2 children with Fetal Alcohol Syndrome in the original Seattle study were both born to the same woman who was black! Black race has also been found to be a major factor in susceptibility to parental alcohol effects and Streissguth et al. state in their conclusions that " the important covariates have been taken into account before claiming a teratogenic effect" when in fact, the covariate for race was not.

For subjects who are mentally retarded using parental school education might be reasonable. But the Streissguth et al. study dealt with trivial differences in IQ scores of 4-year-old children-less than 5 points. If you or I stay up too late at night, our IQ's would probably slip by more than 5 points? If you want to control for parental IQ - measure parental IQ.

What's In A Name?

Not only do we as researchers have to worry about obtaining reliable drinking histories, we need to agree on definitions or criteria for "moderate", "social", "light", and "occasional " drinking. But we still have no consensus in terminology. "Moderate" or "social" drinking in one study can include women who are "heavy" drinkers in another. Even the same research group may use these terms inconsistently. For example, Streissguth and her coworkers defined 4 drinks a day as "social" drinking in one study, 2 drinks a day as "heavy" drinking in another, and "never more than 3-4" as "social" in yet another.

Unrealistic labels have also been used by researchers describing observations in animals. For example, Clarren and Bowden described the amount of alcohol producing blood level of 200-300 mg% in non-human primates as "moderate." Similarily, in their study of alcohol's impact on craniofacial development in mice, Sulik et al. administered dosages of alcohol producing peak BALs of 193-215 mg% and discussed these levels in terms of "social" drinking. If these levels represent "moderate" or "social" drinking, the people drinking this much probably do most of their socializing in a stupor.

What then is an "occasional" or "social" drink? We realize any specific amount is arbitrary. We are prepared to be arbitrary. We suggest that a BAL of less than 0.04% is compatible with "social" drinking. This is equivalent to 2 drinks (containing 1 oz. absolute alcohol) consumed over a 2 hour period for someone weighing 140 lb. We know of no evidence to suggest that this amount consumed occasionally, e.g., once or twice a week, will cause bad things to happen to unborn babies.

What about studies that say spontaneous abortion rates are increased about twofold for women drinking 1-2 drinks per day or less during pregnancy, you say? We say the increased risk in these studies is almost certainly due to the heaviest drinkers who only represent a small proportion of the population - in other words, these studies suffer from the "lies, damn lies and statistics" quandary. In the Harlap et al. study the number of "heavy" drinkers (more than 2 drinks/day) was reported as only 0.5% of the study population. This is a lot less than the national median and modal consumption for pregnant American women. Either the people in this study are an unusual group (which raises other issues of representativeness) or we're dealing with an instance of the "used car salesman" syndrome - women in this study considerably underreported their alcohol consumption. A reasonable interpretation is that the risk for spontaneous abortion was present only among the 2-4% heaviest exposed pregnancies.

Kline et al. retrospectively compared women who aborted spontaneously with a control group and concluded that as little as two drinks a week were a risk factor for spontaneous abortion. While this study controlled for smoking, use of other drugs and diet, it didn't control for social class since all women in this study were on public assistance. When Kline repeated her study with private patients the relation between drinking and spontaneous abortion were no longer there.

Studies of abortion following alcohol exposure in nonhuman primates are very, very consistent in finding that the blood alcohol threshold level for spontaneous abortion is around 205 mg%. In dogs, the BAL threshold is almost identical. These studies in non-human primates and dogs are impressive in their consistency and in their support for suspicion of underreporting in human studies.

How about lowered birth weight, one of the more reliably observed effects associated with in utero alcohol exposure in humans and animals?

In an often cited report, Little found that consumption of 2 drinks per day produced a decrease in birth weight of 160 g. However, drinking ranged from 0 to 5 drinks a day, and 3 of the mothers in this study could have been classified as alcohol abusers. Only seven of the 801 children in the study weighed under 2500 g. Little did not indicate the birth weights of the children born to the alcohol abusers or the drinking behavior of the mothers of the low birth weight infants. It's more than likely that the alcohol abusers accounted for most of the relationship.

In another study alleging to show significant effects of "occasional" drinking, Streissguth and her co-workers reported that eight-month-old children had significantly poorer performances on the Bayley tests after statistical adjustment for a number of confounding variables. However, infants born to women drinking more than 8 drinks per day were lumped in with those whose mothers drank 2 or more drinks per day. When Hank Rosett reanalyzed these data by specific dose and each infant was included only once, only the mental scores of the infants exposed to the higher amounts were significant and their average score was still a normal 98!

Sutton's Law

There is good reason to believe thresholds exist for various adverse alcohol-related birth defects and it's reasonable for clinicians to recommend abstinence to patients contemplating pregnancy or already pregnant. Unfortunately, the patient who places her unborn offspring at greatest risk, i.e., the abusive drinker or alcohol-dependent woman, is the individual least willing or able to identify herself as a risk drinker or to become abstinent.

When someone asked Willie Sutton why he robbed banks, he answered, "That's where the money is..." The occasional or light drinker is like the nickel in the cookie jar. The real loot, in terms of preventing alcohol-related brain damage, isn't in the cookie jar - it's in the vault, in among the risk drinkers. These are the women we must identify and help to become abstinent. Willie had the right idea? Go where the money is.


Dr. Ernest Abel is Professor of Obstetrics and Gynecology in the School of Medicine at Wayne State University.

Dr. Robert Sokol is Dean of the School of Medicine at the same institution. He is past president of the World Association of Pediatric Medicine, is an internationally recognized authority on birth defects, and a consultant to such organizations as the National Institute on Alcohol Abuse and Alcoholism, the Center for Disease control, and the National Institute of Health.

Reprinted with permission of editor and publisher from Engs, Ruth C. (Ed.). Controversies in the Addictions Field. Dubuque, Iowa: Hendall/Hunt, 1990).


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