Why it May Be Okay to Sleep on Your Back During Late Pregnancy

You’ve probably been warned not to sleep on your back while you’re pregnant, but what’s that really all about? Read on for an explanation and—at the end—ideas for making your sleep as comfortable as possible when you are very pregnant.

In a large, prospective study published in 2019, researchers in the United States asked more than 8,700 pregnant women about their sleep habits in their first and third trimesters. This study found no association between sleep position of the pregnant person and adverse events, such as stillbirth or small babies. One caveat is that the researchers did not interview people about their sleep positions after 30 weeks, meaning that its findings might be less applicable after that point of pregnancy.

An editorial that accompanied the publication of the article explains that this larger study is more likely to describe the relationship between maternal sleep position and outcomes in the baby because it is very hard for people to remember what they did after something bad has already happened. Plus, the authors of the editorial write that there is no need to put pressure on moms to sleep a certain way, which might make their pregnancy more difficult and could lead to feelings of guilt and responsibility in case something actually does happen with their baby.

The idea behind not sleeping on your back or right side during later pregnancy is that, as the baby gets bigger, the weight of the baby and your growing uterus could press on your abdomen, potentially compressing internal organs and blood vessels. While unlikely, adverse affects could result from this sort of compression, particularly of the inferior vena cava, which is the main vein that returns blood from your lower extremities to your heart.

The findings of the 2019 study contrast with a study published in 2011. A group of researchers in New Zealand asked women who had just experienced stillbirth and women matched to their gestation with ongoing pregnancies what their sleep position had been at the beginning of the night—left side, right side, on their back, or something else—the night before the interview or the stillbirth. The authors found that, even when they tried to eliminate other factors that could confound the results, back and right side sleeping were both associated with a greater risk of stillbirth. They called for further research to confirm the results, but care providers started to advise pregnant people to sleep on their left sides right away.

Since that original study in 2011, researchers and care providers have raised questions about its validity and there have been other studies that looked more in depth at this issue. One study in 2014 pointed out that the original 2011 research, as well as two subsequent studies that to some extent corroborated the first paper’s findings, asked parents to self-report their sleep position. The 2014 research found that people’s reports of their sleep positions were fairly accurate overall, but that individual accuracy varied quite a bit. It’s also important to note again that all of these studies that made a link between maternal sleep position and outcomes for the baby asked people about their sleep position after an adverse event had already happened, when they might not remember exactly what happened or might mis-remember in order to assign meaning to something in their own behavior.

So what should you do? Earlier studies suggest that there might be a link between maternal sleep position and adverse outcomes for babies, but the largest, most recent and well-controlled study shows that the concerns about sleeping on your back may be unwarranted. Helpful analysis of the original study from the Cleveland Clinic points out that in the 2011 study, most people slept on their backs the entire night without even getting up to use the bathroom. Since most pregnant people change positions and get up to pee several times per night, the findings may not represent the experience of most people.

Overall, it’s important to get as much sleep as you can while pregnant. You need sleep to deal with work and life and it helps your immune system stay strong to fight infections. In order to sleep as well as you can during pregnancy, there are a few things you can try:

  • Pregnancy pillows can help you position your body for increased comfort as your baby grows. If you’re used to sleeping on your stomach or back, but no longer feel comfortable in either position, sometimes you can use a pregnancy pillow or just regular pillows to get into a side lying position that feels like you are tummy or back down.
  • You may already have cut back your caffeine usage, but paying attention to when you have it can also help improve sleep. Having less caffeine late in the day might work for you.
  • Get your exercise. Walking, swimming, hiking, yoga: all of these can help you sleep better at night. Stretching especially can help with aches and pains that lead to discomfort and wake you up.

Abby Olena
Dr. Abby Olena has a PhD in Biological Sciences from Vanderbilt University. She lives with her husband and children in North Carolina, where she writes about science and parenting, produces a conversational podcast, and teaches prenatal yoga.

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