Is Sleeping on Your Back During Pregnancy Dangerous?

If you are pregnant and used to sleeping on your back, you may want to get used to a new sleep position now, since it's not recommended for pregnant people to sleep on their back after 20 weeks of pregnancy. When you lie on your back, the weight of your uterus can compress a major blood vessel that runs down near your spine called the vena cava. The theory is that compressing the vena cava can disrupt blood flow to the fetus, so in general, most doctors recommend avoiding compressing the blood vessel while you sleep.

Pregnancy is often a time full of new sleeping positions. In addition to avoiding sleeping on their back, many pregnant people find that they need to adjust their sleeping positions as their belly grows, especially in the third trimester. Getting comfy can be a challenge when you're growing a human!

Here are more tips for getting a good night's rest while pregnant.

The Best Sleeping Position During Pregnancy

The best way to sleep during the second half of pregnancy is on your side. Some doctors recommend the left side over the right because the vena cava is located to the right of your spine, so sleeping on your left side allows blood to flow more freely to your fetus. However, this shouldn't make a big difference, and it's more important that you pick whichever side feels better. Sleep is important for both your and your baby's health, so choose comfort over a "better side" for this one.

If you need help adjusting to side sleeping, try supporting different parts of your body with a variety of pillows. You can pick up a specific pregnancy pillow, or use several regular pillows to prop yourself up. For instance, one pillow between your knees and another below your hips can help you balance on your side more easily. You can also test out sleeping with a full-body pillow placed behind your back or in front of you, or experiment with a wedge-shaped pillow, propping it under your side or chest.

Another tip: If you're waking up with aches, a firmer mattress might be the answer. Memory foam supports your torso and limbs and could make it easier to sleep in a position that is new to you.

What If I Wake Up on My Back While Pregnant?

Should you wake up on your back in the middle of the night, don't worry—your baby is perfectly safe. Your body would get dizzy and nauseous before your baby was in any real danger of not getting enough oxygen. Plus, in most cases, being pregnant will be its own built-in protection for your baby, because by the time your uterus is heavy enough to compress the vein, you'll be so uncomfortable lying on your back that your body will flip over, even if you're asleep.

What the Research Says About the Link Between Stillbirth and Sleep Position

There are some studies that have found a small link between stillbirth and sleep position, but overall, there is no compelling evidence that occasionally or accidentally sleeping on your baby during pregnancy will hurt your fetus.

The associations are from a few studies:

• In a 2017 study, researchers from the University of Auckland found that pregnant people who sleep on their backs during their third trimesters may also be putting undue stress on their fetuses—which might, in turn, increase stillbirth risk.
• A 2011 study that involved 500 pregnant women also suggested that sleeping in the supine position might increase the risk of late stillbirth—though other pregnancy complications may have affected these results.
• A 2019 study published in The Lancet also concluded that if all pregnant people avoided sleeping on their back during pregnancy, the risk of stillbirth would be reduced by 6%.

However, the researchers behind the 2019 study also pointed out that there are many different risk factors that could contribute to stillbirth in pregnant people who sleep on their backs, such as obesity, smoking, or other medical conditions.

Additionally, there was no link to stillbirths in pregnant people who woke up on their backs, only those who regularly went to sleep on their backs because they spent the most amount of time on their backs. In other words, as long as you're doing your best to go to sleep on your side, if you wake up on your back once in a while, there's no reason to worry.

Sean Daneshmand, M.D., an OB-GYN and the founder of Miracle Babies, also offers some reassurance. "This was a study on low-risk patients with a very small sample population without any difference in pregnancy complications or newborn outcomes," he says. "Given the very low incidence of stillbirths and the very high likelihood that majority of [pregnant people] can relate to falling asleep on their backs at one or more times during their pregnancy, I do not think this is something of concern."