Can I Sleep on My Back During Pregnancy? What the Research Actually Says
Written and reviewed by Anna McMaster, PT, DPT, PRPC
As your body changes during pregnancy, getting comfortable at night can become increasingly challenging. One of the most common questions pregnant women ask is about sleep positions — specifically whether it's safe to sleep on their back, and whether they really have to sleep on their left side only. Let's look at what the research actually says, because the answer is more nuanced than you might have heard.
Why Back Sleeping Becomes a Concern
As your uterus grows, lying flat on your back can cause it to compress the inferior vena cava (IVC), the large vein that carries blood from your lower body back to your heart. This can reduce blood flow to the uterus and placenta.
Research has found that sleeping on your back in the third trimester is associated with reduced blood flow to the uterus, changes in fetal heart rate patterns, potential reduction in birth weight, and a higher risk of stillbirth. These are real findings and worth taking seriously, but they come with important context.
Most of this research focuses on the third trimester, specifically after 28 weeks. Many healthcare providers recommend beginning to shift away from back sleeping around 20 weeks, when the uterus becomes heavy enough to potentially compress major blood vessels. If you're in your first or early second trimester, back sleeping is generally considered fine.
Do You Have to Sleep on Your Left Side?
Left side sleeping has traditionally been recommended during pregnancy because it takes pressure off the liver and kidneys, maximizes blood flow to the placenta, and may help reduce swelling in the hands, ankles, and feet.
However, newer research has updated this guidance. A 2019 study found that sleeping on either the left or right side appears to be equally safe for most of pregnancy, particularly before 28 weeks. So if you're more comfortable on your right side, you don't need to force yourself onto your left. Both sides are a good choice.
What to Do If You Wake Up on Your Back
This is one of the most common sources of anxiety for pregnant women and the answer is reassuring: don't panic. If you wake up and find yourself on your back, simply roll to your side and go back to sleep. The research on back sleeping risk is primarily about going to sleep on your back, not momentarily ending up there during the night. One study specifically looked at the position women were in when they fell asleep and found this to be the more significant factor.
To make it easier to stay on your side, positioning a pillow or rolled blanket behind your back can help prevent you from rolling over during the night. A pillow between your knees and one supporting your belly can also make side sleeping more comfortable and sustainable through the night.
Listening to Your Body
Pay attention to how you feel in different positions. If you experience dizziness, shortness of breath, or discomfort while lying on your back, that's a clear signal to change positions. These symptoms can indicate that circulation is being compromised and your body is telling you something useful.
If you're finding it increasingly difficult to get comfortable at night as your pregnancy progresses, a pelvic floor PT or pregnancy-specialized physical therapist can help you troubleshoot your sleep setup and address any musculoskeletal contributors to discomfort.
The Bottom Line
Side sleeping is the safest choice from around 20 weeks onward, and both left and right sides are equally acceptable. Avoid going to sleep flat on your back as your pregnancy progresses, but don't stress if you wake up there — just roll over and settle back in. Every pregnancy is different, and the goal is finding a position that supports good circulation for you and your baby while also letting you actually rest.
For personalized support with sleep comfort and pelvic health throughout pregnancy, Amie offers programs designed by pelvic floor PTs for every stage of your journey.
References
Anderson N.H., et al. (2019). Association of supine going-to-sleep position in late pregnancy with reduced birth weight: a secondary analysis of an individual participant data meta-analysis. JAMA Network Open, 2(10), e1912614.
Cronin R.S., et al. (2020). Associations between symptoms of sleep-disordered breathing and maternal sleep patterns with late stillbirth. PLoS One, 15(3), e0230861.
Humphries A., et al. (2019). The effect of supine positioning on maternal hemodynamics during late pregnancy. Journal of Maternal-Fetal & Neonatal Medicine, 32(23), 3923-3930.
Robertson N., Okano S., Kumar S. (2020). Sleep in the supine position during pregnancy is associated with fetal cerebral redistribution. Journal of Clinical Medicine, 9(6), 1773.
Stacey T., et al. (2018). Going to sleep in the supine position is a modifiable risk factor for late pregnancy stillbirth. BJOG: An International Journal of Obstetrics & Gynaecology, 125(2), 254-262.
Wilson J., et al. (2021). A position modification device for the prevention of supine sleep during pregnancy: a randomised crossover trial. BJOG: An International Journal of Obstetrics & Gynaecology, 128(7), 1159-1168.