It’s science: Why pregnant women should sleep on their left side

Towards the end of my twin pregnancy, all I wanted to do was lie on my back. The whole “sleep now because you’ll never sleep again” adage was lost on me—I just couldn’t get comfortable on my side, and since that’s the only way pregnant women are supposed to sleep, I wasn’t logging much shut-eye. I’d wager I’m not the only mom who dealt with this common third-trimester issue.

The recommendation that side-sleeping (specifically left side sleeping) is the safest option during pregnancy is pretty well-known, and the risk of sleeping on your belly during pregnancy seems pretty obvious (you wouldn’t want to crush that sweet baby!).

But why is the left side preferred to the right?

Let’s start with why medical professionals want pregnant women to become side sleepers.

According to the American Pregnancy Association , there are a few issues that can arise when a mom-to-be sleeps on her back. They range from pretty benign, like backaches (which, let’s be frank, are sort of par for the course during pregnancy no matter how you sleep), to much more serious, like low blood pressure.

The more serious issues from back sleeping arise from the weight of your the growing belly on your intestines and major blood vessels, as this can decrease circulation to your baby. A 2015 study from Sydney suggests sleeping in the supine position may even up the odds of stillbirth. A 2017 study from the University of Auckland found a similar correlation. And just this year, research from the University of Huddersfield found a link between back sleeping after 28 weeks and stillbirth as well.

Those seem like pretty compelling reasons to stay off your back (no matter how much relief that particular sleep position gives you!) until after you’ve delivered. But does that mean you have to switch up your sleeping position as soon as you see those two pink lines? Not necessarily—you’re likely in the clear until your baby gets a bit larger, and we’d recommend chatting with your doctor to pinpoint a time in your pregnancy when you should embrace side-sleeping.

When it comes to pregnancy sleep, the left side is the…well, ‘right’ way to go, at least according to many experts.

According to physician-reviewed information from KidsHealth , sleeping on your left side helps keep weight off your liver (which is located on the right side of the body) and improves blood flow and circulation to major organs. However, researchers from the University of Huddersfield’s study didn’t find any reason to believe there’s a difference in stillbirth risk if you sleep on your left side over your right.

The bottom line here? If sleeping on your right side is significantly more comfortable for you, you should run this by your doctor—if they’re on board, it could be a perfectly safe solution—but you may want to adjust to sleeping on your left side if possible.

But mamas, hear us out: If you do wake up and realize you’ve migrated in your sleep, you shouldn’t beat yourself up (it happens!). Oh, and some anecdotal advice? Invest in a pregnancy pillow. A good one will help you stay on your side and keep you (relatively) comfortable.

With pregnancy, knowledge is power. Motherly’s evidence-based, women-centered books and classes can help you feel as empowered as possible.

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