Emily Oster stirred a lot of controversy when she suggested that pregnant women could enjoy a drink of alcohol if they so chose. Why did she arrive at a view that clashed with much of the American medical establishment? She named two reasons. The first is that she did a better job of sifting through the evidence than the medical experts had done. More importantly, she was actually trying to communicate the facts. Many others are practicing deception-based medicine.

She explained in Expecting Better:

But the bigger thing, I think, is the concern (which was expressed to me over and over by doctors) that if you tell people they can have a glass of wine, they’ll have 3 (or one giant “bowl-o-wine”). Even if one isn’t a problem, three are. Better to say you can’t have any, as that rule is easy to understand.

Oster did a tremendous amount of research before concluding that a little wine is okay. But it doesn’t take skills like Oster’s to verify that mothers are oversold on the dangers of moderate drinking. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) has a website where they answer questions in an easy to understand manner. The first question under “Drinking and Your Pregnancy” is “Can I drink alcohol if I am pregnant?” The response:

No. Do not drink alcohol when you are pregnant. Why? Because when you drink alcohol, so does your baby. Think about it. Everything you drink, your baby also drinks.

This response is a rejection of scientific thinking. How could pregnant women possibly know whether mild amounts of alcohol were beneficial or detrimental to the human fetus without reviewing medical research? Given that moderate alcohol consumption might be beneficial for adults, there is no obvious reason mothers should know that it will be bad for the fetus.

Despite their overly simplistic advice to mothers, the NIAAA is not a mindless critic of drinking. Other parts of their website contain dispassionate science:

Women who give birth to FAS … children generally practice frequent and protracted binge drinking, which produces high blood alcohol concentrations. Although a majority of women in many studies reduce their alcohol consumption during pregnancy, mothers of FAS children generally do not … Most women who give birth to FAS children live within a social and cultural milieu that tolerates, condones, or is ineffective in dealing with problem drinking.

In another section of the NIAAA website:

The minimum quantity of alcohol required to produce adverse fetal consequences is unknown … Clinically significant deficits are not common in children whose mothers drank less than approximately five drinks per occasion once per week …

So why is the NIAAA so categorical when they advise expectant mothers not to drink? Interestingly, they provide the answer in their scientific summary:

Despite the many gains in knowledge, we still do not know if there is a “safe” dose of alcohol that can be consumed by pregnant women without risking damage to their unborn children. Until such a safe dose, if it exists, can be determined, the only responsible advice to women who wish to become pregnant and to those who are pregnant is to avoid alcohol use entirely.

This might be plausible. However, the case for zero alcohol can be made without urging women to rely on their biological intuitions.

In any event, the NIAAA clearly has two messages tailored to two different audiences. On the one hand, they dispassionately explain the state of science using a small font, dense text, and the language of the specialist. Here they admit that much ignorance and confusion exists. On the other hand, they unambiguously advise expectant mothers to abstain from drinking alcohol as if the science was a settled matter. This is written in easy-to-understand language with lots of white space. This example illustrates a common phenomenon. Ordinary people do not receive medical information in an unbiased manner. Instead, medical research is frequently passed through a filter so that it provides only what is prudent to believe. Seemingly, the unspoken belief is that people can’t handle the truth.

Completely exonerating moderate drinking with scientific data would be a daunting task. Making such an exoneration less likely is the fact that scientists may not be looking very hard. As Robin Room asserts in The Lancet:

But there has been little research on what a safe level might be, or just what are the risks of occasional drinking (with no binge spikes). The scientific agenda seems to be set by an implicit social policy judgment that the issue is better left unsettled: any answer other than zero would undercut the justification.