Drinking in Pregnancy

August 20th, 2012 by Potato

A friend linked to an article on drinking while pregnant, which sparked a spirited discussion on Facebook. I thought I’d go off on a bit of a tangent here, where the discussion is a bit more open (and where I can add in graphs).

I don’t have the free time these days to dig around in the literature to get fully up-to-speed, but basically here’s the science as I know it on drinking in pregnancy: it’s bad. We know that completely abstaining is our baseline: most moms-to-be are cautious and do this. And, we know that drinking a lot is bad. In-between, there isn’t a lot of good data: it may be a little bit bad to drink a little bit, or it may have no effect until some threshold has been hit, or it may even be slightly beneficial (as this recent article suggested). So there are some big error bars in the middle there.

To pick on this study in particular, it was a retrospective study that asked women what they drank during pregnancy many months after they had given birth. Though this kind of study can be insightful and guide further research, I wouldn’t be overturning a cautious, conservative hypothesis on that kind of data. I would caution moms-to-be out there to not go out and have a drink or two on the basis of a study like this.

This is how science works, generally: you get a weak-ass study that nonetheless is cheap to do and suggests something interesting, so you get some funding and ethics approval, and do a better study, and change your ideas of how the world works as the data comes in. But real-world considerations do get in the way sometimes.

A stronger study would be one with randomization, controlled variables, etc. The thing is, it’s unethical to run that kind of study, and I don’t know if there are good animal models for the more subtle forms of alcohol-related damage, due to the unique nature of frontal cortex development in humans. Plus, there isn’t really a demand for such a study: it’s not hard to abstain from drinking for 9 months. No serious scientist wants to spend time trying to find out what the safe limit is for alcohol in pregnancy when there are so many more pressing problems to address. Nobody would want to fund it: even the brewing companies wouldn’t touch it since even if you did show beyond a doubt that drinking some amount was safe (nay, beneficial), there would be a negligible effect on alcohol sales (if it found 1 drink/week was safe, that’s not even two cases of beer for the whole 9-month pregnancy). And it could be an expensive study if you were to follow a cohort of several thousand kids to age 10 or something in order to detect potentially subtle changes in IQ and social development.

So we’re stuck with imperfect information. We know the two ends of the curve fairly well, but have imperfect information for what lies in the middle. Our simple linear assumption may not be correct, but guessing wrong has consequences. In that case, the conservative thing to do is to assume that there is no safe level, and abstain completely. Which is what the current recommendations are.

An analogy would be radioactive materials: we know that a large amount of ionizing radiation is bad: it causes cancer, radiation sickness, necrosis, and death. We’ve seen it in accident victims and those near the WWII-era bombings and tests. But even with good animal models it’s hard to study the in-between doses. Once again we have a case with really good data at the extremes of the chart, but gaps and poor data in the middle leaving open the question of what the response looks like at intermediate doses. There is a hypothesis (called radiation hormesis) that small amounts of radiation are actually good for you, and there are some people testing that out… but there isn’t really a market for that study, either. So the principle of keeping the dose As Low As Reasonable Achievable (ALARA) is employed for those working with radioisotopes. For drinking, ALARA is zero: there is no “background level” of alcohol exposure; being pregnant is very unlike being a nuclear medicine technologist. It is very easy/achievable to just not drink while pregnant. I have no sympathies for someone who can’t abstain when presented with a good reason to do so (e.g.: someone who needs to drive somewhere, is pregnant, or is on call for some demanding job).

Now the point was raised in that long Facebook back-and-forth that women suffer a lot of second-guessing and judgment by people for what they put in or do with their bodies while pregnant. It can be harsh and unfair. For many things, yes, yes I think it is, especially since there are so many little things you’re supposed to do these days, and no one can ever be perfect (not even a pregnant woman).

One person suggested it was a double-standard to criticize a woman for drinking but not for a midnight ice cream pig-out. To that I say: there isn’t fetal mochaccino syndrome, or infant chocolate disorder (indeed, chocolate consumption seems to be beneficial), while there is fetal alcohol syndrome (and just as importantly, widespread knowledge thereof). So it’s a totally different thing to look down on someone drinking, smoking, or shooting heroin than it is to judge someone for pigging out, drinking caffeine, using a cell phone, or skipping the seafood portion — I wouldn’t consider it a double-standard at all.

As much time as I spend here turning over conventional wisdom with evidence, in this case I think the evidence is not definitive and the best course of action is to continue to abstain from drinking while pregnant.

2 Responses to “Drinking in Pregnancy”

  1. netbug Says:

    I like this post, and I agree, but I still have trouble with the idea that 1 glass of wine is going to do more damage than 1 carton of ice-cream.

  2. JP Says:

    Very well written argument!
    While ideally one could put every pregnant woman in a pregnancy boot-camp for 9 months where exercise, diet, and vices could be controlled, the idea is laughable. Unless, it was self-imposed of course.
    As for the diet versus drugs argument, I think we need to keep in mind that for the most-part ice cream is composed of normal dietary building blocks. Perhaps not in the ideal quantities or balance, but nonetheless. I also believe that, for the most part, the drugs Potato is talking about cross the blood-brain barrier and can have damaging effects. Most of the problems caused by a bad diet can be reversed. However, the same can’t be said for problems that arise from alcohol (for example), particularly at the delicate early stages of neural development. One cell, at an early enough stage could proliferate into a larger portion of brain tissue. Do you want to risk the consequences of damaging it?