Doctors often warn against sleeping on your back during pregnancy, and some go so far as to suggest favoring your left side. It’s really a cherry on the top of pregnancy’s many discomforts: Imagine trying to sleep while housing a kicking, rolling, sucker-punching basketball-sized fetus without feeling able to turn over. The thinking behind said advice is that back sleeping could compress the blood vessels to the uterus and cause pregnancy complications, and that left-side sleeping increases circulation. Now, though, a new study suggests that, eh, maybe never mind. Maybe you don’t need to endure sleep-based torture.
The study, published in the journal Obstetrics & Gynecology, looked at outcomes for nearly 9,000 women before they reached the 30-week mark of their pregnancies. The researchers found that 22 percent experienced complications, but as Reuters reports, “women who slept on their right side or on their back were no more likely to experience serious complications than women who slept on their left side.” That sentence right there is a perfect and horrifying encapsulation of the degree of regulation, monitoring, and restriction around pregnancy. We’re not just talking about back sleeping, but also what side, right or left, pregnant people sleep on.
Back sleeping is just one of countless activities that doctors frequently caution against—with varying degrees of reliable statistical backing—in the name of protecting the fetus. For example, staying away from alcohol, limiting caffeine, and avoiding a relaxing hot tub. (Essentially, spurning the good things in life.) These numerous, and frequently hazy, cautions are part of why economist Emily Oster wrote her deeply-researched 2014 book Expecting Better: Why the Conventional Pregnancy Wisdom is Wrong and What You Really Need to Know, which attempted to sort through the tricky science on pregnancy prohibitions. Naturally, she had to tackle the sleep positions question and wrote in a 2013 advice column for Slate that research had actually raised questions about the reigning wisdom about sleep positions:
In one very good study, researchers had pregnant women lie on their backs, and they measured blood pressure and the blood flow to the uterus. They found that lying down has no particularly bad impact on blood flow. A couple of women in that study became uncomfortable but felt better when they changed positions. The authors conclude that some women might be uncomfortable sleeping on their backs, but if you are not one of them, you should feel fine about it.
Shortly thereafter a review of relevant research crunched the numbers and found that “the advice often given to pregnant women to lie on the left side is... not relevant.” More recently, though, research has suggested that sleeping on your back during late pregnancy could double the risk of stillbirth. However, researchers, including one of those behind the latest study, have questioned some of the research methods. Now, this latest study raises further questions about cautioning pregnant people off back-sleeping, although it does have its own limitations, given that it only looked at pregnancies up to 30-weeks gestation.
In an editorial published in the same issue of the journal Obstetrics & Gynecology, Oster herself, along with Nathan Fox, a specialist in maternal-fetal medicine, write, “We suggest that pregnant women should be told that, although some evidence in the past may have suggested a link between not sleeping on the left side and adverse outcomes, the best evidence does not suggest such an association, and, as a result, they should feel comfortable sleeping in any position that works for them.” (Emphasis mine.) They add that the “contrast been these new results and the existing advice should also give pause in how we generally approach recommendations and guidelines for pregnant women in the face of limited evidence.”
Of course, with any pregnancy cautions, there is the emotionally persuasive argument of “better safe than sorry,” but it is disproportionately easier for doctors to “play it safe” with their recommendations than it is for a pregnant person to do so with their behavior 24/7—literally, because we’re talking about sleep positions—and for nine months straight. Besides, “playing it safe” isn’t always as straightforward as it seems. In an interview last year, Karen Gibbins, one of the researchers behind the current study, pointed out, “It is hard enough to get pregnant and to sleep well. The stress caused by trying to sleep in a position that is unnatural to you is more likely detrimental in my mind than the act of sleeping on your back.”
Later in the interview she clarified that stress isn’t good for the fetus—but it isn’t good for the person carrying the fetus, either. It is that fetus-carrier—and their stress, sanity, convenience, and comfort—that is typically forgotten in these recommendations. Pregnancy is so often an exercise in fear-based behavior modification: All these many warnings don’t just mean missing out on good shit like sushi and Hollandaise sauce—but also, more meaningfully, they result in the psychic toll of constant, terrified self-monitoring.
Experts often err on the side of caution, because they can, why not. Meanwhile, fetus-carriers are left to parse complicated data, and keep up on evolving science, to determine the actual, relative risk of, well, most anything they might do in the course of living their lives as, apparently, no longer fully autonomous human beings.