Is It Safe to Sleep on Your Back During Pregnancy?

As your pregnancy progresses, getting enough sleep becomes vitally important—for both you and your baby. And yet, catching zzz's can sometimes feel elusive, especially when you learn that you probably shouldn't sleep on your back while pregnant.

If you're traditionally a back sleeper, you may be wondering why you need to avoid this sleeping position, especially in the third trimester. The primary reason is that sleeping on your back puts stress on a vein called the vena cava. This could reduce blood flow to your baby, potentially resulting in complications like decreased oxygen supply, preeclampsia, and fetal growth problems.

Below we take an in-depth look at why sleeping on your back while pregnant can be dangerous. Plus, we offer tips for getting a good night's rest in every trimester.

Is It Safe to Sleep on Your Back While Pregnant?

If you're pregnant and used to snoozing on your back, you may want to get used to a new sleep position now, as it's not recommended for pregnant people to sleep on their back after 20 weeks of pregnancy.

What's the reason for this? The weight of your uterus can compress a major blood vessel that runs down near your spine called the vena cava. Compressing this vessel can disrupt blood flow to the fetus.

A back-lying sleep position may ultimately interrupt the vena cava's ability to return blood from the abdomen to the heart and affect the baby's oxygen supply, says Shelby Harris, PsyD, a psychologist who is board-certified in behavioral sleep medicine (BSM) by the American Academy of Sleep Medicine.

Studies have linked compression of this vein to a number of potential complications including preeclampsia, reduced fetal growth, and stillbirth. The pregnant person may also feel dizzy, according to the American College of Obstetricians and Gynecologists (ACOG).

Best Sleeping Position During Pregnancy

During the second half of pregnancy, the best sleep position is on your side. Some health providers 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.

That said, 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.

"Sleeping in the side position helps the baby get enough oxygen and nutrients, and it also keeps your organs from getting squished," says Dr. Harris. "If you have any concerns or medical issues, talk to your doctor for advice tailored to your needs."

What If I Wake Up on My Back While Pregnant?

If 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.

"If you do wake up on your back, don’t stress about it and just turn back to the side position," says Dr. Harris. "Worrying about your sleep position can make it even harder to sleep, so don’t stress if you end up on your back—just gently shift back to your side."

Plus, in most cases, being pregnant will be its own built-in protection for your baby. 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 Research Says About Stillbirth and Sleep Position

It's important to note that evidence of back-sleeping dangers isn't very conclusive. There are some studies that have found a small link between stillbirth and sleep position, but overall, there's 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, researchers also pointed out that many different risk factors 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, MD, 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."

Still, most providers recommend side sleeping to prevent any possible complications that might emerge.