Sleeping on your right side during pregnancy is safe. Most experts now agree that either side provides good blood flow to your baby, and recent research shows no meaningful difference in risk between left-side and right-side sleeping. The old advice to sleep exclusively on your left side has softened considerably as newer studies have come in.
Why Side Sleeping Matters in Pregnancy
As your uterus grows, it becomes heavy enough to press on major blood vessels when you lie flat on your back. The biggest concern is compression of the inferior vena cava, the large vein that carries blood back to your heart from your lower body. When that vein gets compressed, it can reduce the amount of blood returning to your heart, lower your cardiac output, and decrease blood flow to the placenta. In rare cases, prolonged back sleeping in late pregnancy has been linked to a higher risk of stillbirth.
Side sleeping, whether left or right, shifts the weight of the uterus off that vein. That’s why the core recommendation is to avoid spending long stretches flat on your back in the third trimester, not to favor one side over the other.
Left Side vs. Right Side
For years, pregnant people were told to sleep on the left side specifically, based on the idea that it maximizes blood flow because the inferior vena cava runs slightly to the right of the spine. In theory, lying on the left should take the most pressure off that vein. And while the left side is probably the absolute ideal position, the practical difference between left and right is small.
A large analysis found that going to sleep on the right side carried nearly identical odds of complications compared to the left, with an adjusted odds ratio of 1.04 and no statistically significant difference. In plain terms, researchers could not detect any added risk from right-side sleeping. As one Cleveland Clinic physician put it: if you’re truly on your side, you’re going to get good blood flow regardless of which side you choose.
When Sleep Position Starts to Matter
Sleep position doesn’t appear to be a concern during the first and second trimesters. An NIH-funded study found that sleeping on your back or either side through the 30th week of pregnancy did not increase the risk of stillbirth, reduced birth size, or high blood pressure disorders. The researchers noted that their data only covered up to 30 weeks, so they couldn’t draw conclusions about later pregnancy.
Six observational studies have linked back sleeping (not side sleeping) with a higher risk of stillbirth after 28 weeks. That’s why most guidance focuses on the third trimester, roughly from week 28 onward. Before that point, sleep however you’re comfortable.
What to Do If You Wake Up on Your Back
This is one of the most common worries, and it shouldn’t be. Waking up on your back does not mean you’ve harmed your baby. Short periods on your back, even an hour or two, are unlikely to cause any lasting harm. Your body has built-in warning signals: if back sleeping is reducing your blood flow enough to matter, you’ll typically feel it. Your heart may beat faster, you might feel short of breath, or you’ll feel dizzy or uncomfortable. Those sensations will usually wake you up or prompt you to roll over before any real problem develops.
If you wake up on your back in the middle of the night, simply roll to either side and go back to sleep. There’s no reason to panic or lose sleep over it.
Staying Comfortable on Your Side
The bigger challenge for most pregnant people isn’t choosing a side. It’s staying comfortable long enough to actually fall asleep. As your belly grows, side sleeping can strain your hips, lower back, and pelvis. A few simple adjustments help.
- Pillow between your knees: This keeps your hips aligned and takes pressure off your lower back and pelvis. A regular pillow works fine.
- Support under your belly: A small pillow or rolled towel tucked under your bump prevents it from pulling you forward and straining your back.
- Pillow behind your back: If you tend to roll onto your back during sleep, wedging a pillow behind you can keep you tilted to the side.
- Full-body pregnancy pillows: C-shaped or adjustable pregnancy pillows support your belly, back, hips, and legs simultaneously. They can be positioned to cradle whichever side you prefer.
You don’t need to stay locked on one side all night. Switching between left and right is perfectly fine and can actually help with hip soreness. The goal is simply to avoid long stretches flat on your back in the third trimester. Any side position counts.