Is drinking during pregnancy really so bad?

The American Academy of Pediatrics reaffirmed its stiff stance on alcohol this week, urging pregnant women to give up drinking entirely. No exceptions for slow-sipped glasses of red wine, occasional nips of scotch, or celebratory champagne.

While this may seem familiar advice, the evidence is actually mixed. The Academy of Pediatrics concedes that while heavy drinking can severely harm developing babies, there’s no such consensus about the effects of occasional alcohol consumption. In fact, several recent studies have concluded that casual drinking is largely benign.

But the new policy is guided by precaution. Given that we don’t know where the line is between safe drinking and dangerous drinking — one glass of wine per day? one per week? — the only way to ensure that pregnant women don’t have too much is to recommend that they have nothing at all.

How dangerous is alcohol consumption during pregnancy?

Decades of research have demonstrated the terrible impact alcohol can have on developing babies. Among other things, in-utero exposure can lead to stunted growth, changes to the shape of the lips and eyes, various learning disabilities, and attention problems. Collectively, these conditions fall under the heading of fetal alcohol syndrome, or sometimes the broader category of fetal alcohol spectrum disorders.

The Centers for Disease Control estimates that only about 0.1 percent of all children in the United States have fetal alcohol syndrome, but the American Academy of Pediatrics suggests that this is likely a significant underestimate.

Precise numbers are hard to find since the physical effects of fetal alcohol syndrome are often subtle, and the cognitive impact can take years to manifest.

Can this really happen from occasional drinking?

Perhaps, but it’s not clear.

It does seem that the risks increase as alcohol consumption goes up. Binge drinking is worse than moderate drinking, and drinking through all three trimesters is worse than just one.

Lacking, though, is any strong sense of when problems really take hold. The AAP cites a study from 1984, suggesting that as little as one drink per day can affect infant growth. But several more recent, international studies have found that low levels of alcohol consumption have no impact on fetal health or later childhood development.

So why advise against all alcohol consumption?

It’s all about balancing risks and rewards. And the trick with occasional drinking is that even if the risks are low, the rewards are, too.

It would be different if alcohol served some clear, positive function. Compare it with driving, for instance. That is a fairly risky activity, but no one tells pregnant women not to drive, because they need to get around. Or consider prescription drugs, also potentially risky, but still prescribed if essential to the mother’s health and well-being.

Alcohol consumption is different. It does have its benefits — like stress relief, gustatory pleasure, and smoothed sociability — but nothing urgent or essential enough to make a nine-month hiatus seem a terrible hardship.

Is there space for skepticism?

Not every pediatric organization in the world agrees with the American Academy of Pediatrics. The United Kingdom’s Royal College of Obstetricians and Gynecologists advises against drinking during the first trimester, but adds that small amounts probably aren’t harmful during the later stages.

Also, there have been times in the past when warnings about the risk of drug use by pregnant women turned out to have been exaggerated. During the crack scare of the 1980s, there was widespread concern about “crack babies” and the damage crack cocaine could inflict on a developing fetus. But a multidecade study of those kids has found almost no evidence of harm. They learned, grew, and moved through life, very much like their non-exposed peers.

It’s still not a good idea to use crack cocaine while pregnant, given that the drug has lots of dangerous side effects, but these findings are a reminder that we don’t always do a good job of anticipating or evaluating risks.

One thing the crack study found, for instance, is that while the kids weren’t much affected by their exposure to drugs, they were terribly afflicted by poverty. Being poor did more to hurt those kids than the cocaine, and today more than one in five US children grows up in poverty.

So, what’s the takeaway?

Medical professionals and the pregnancy-advice industry have assembled a host of restrictions on pregnant women: no deli meat, no soft cheese, no swordfish, no sushi, no strenuous exercise, no hot tubs, and, according to the American Academy of Pediatrics, absolutely no alcohol.

The logic behind this prohibition on drinking is clear: Since we really don’t know what constitutes a safe level of alcohol consumption, the only way to avoid the risk entirely is to avoid the alcohol.

That doesn’t mean that the case against casual drinking is overwhelming — it isn’t. But in the absence of clear evidence, the thinking of the medical establishment is that what you don’t imbibe can’t hurt you.