Do pregnant women have to sleep only on their left side? The right sleep position by stage of pregnancy, without lying stiff all night

“Sleep on your left side, dear, never on your back.” Many moms hear this from the moment they find out they’re pregnant. Then they end up lying stiff all night, and waking in the middle of the night to find themselves sprawled on their back gives them a jolt of fear that something might have happened to the baby.

Take it easy first. This doesn’t need to be that stressful. Let’s look at what the advice really is, when it starts to apply, and how to sleep comfortably without checking on yourself all night.

Do you really have to sleep only on your left side?

Quick Answer: No. Left or right are both fine. Current evidence hasn’t clearly found that the left side is safer than the right.

The UK’s NHS says the safest position to go to sleep in is on your side, left or right. Tommy’s, an organization that campaigns on this issue, also concludes that the left side hasn’t been clearly shown to lower the risk more than the right.

The reason you often hear is the worry that the growing uterus will press on a blood vessel. The elders who tell us this really do mean well, and there’s nothing wrong with sleeping on your left. But if you’re more comfortable on your right, don’t force yourself to switch.

From how many weeks should you not sleep on your back?

Quick Answer: The advice to go to sleep on your side applies from 28 weeks onward. Before that, sleep in whatever position is comfortable.

Gestational age	Sleep position
First trimester (to about 13 weeks)	Any comfortable position, including on your back or stomach
Second trimester (about 14 to 27 weeks)	No restriction like in the third trimester yet. Many moms start practicing side sleeping to get used to it
From 28 weeks	Go to sleep on your side, left or right

So the second trimester is a good time to try arranging pillows and practice sleeping on your side, so you don’t have to adjust all at once when you reach 28 weeks.

Why you shouldn’t go to sleep on your back after 28 weeks

Quick Answer: Because going to sleep on your back after 28 weeks is linked to a higher risk of stillbirth. It’s thought to be related to blood flow and oxygen reaching the baby.

The evidence summarized by Tommy’s is that going to sleep on your back in late pregnancy is linked to a risk of stillbirth about 2.6 times higher compared with sleeping on your side.

That may be unsettling to read, but please look at the big picture too. The baseline risk here is already low (in the UK, about 3 in 1,000 births). Sleeping on your side is one of the simple things that can lower the risk further. It’s not something you need to lie awake watching yourself over all night.

What to do if you wake up on your back

Quick Answer: Don’t panic. Just roll back onto your side and go back to sleep. The research mainly looks at the position you go to sleep in, not every movement during the night.

Everyone turns over in their sleep. Nobody can control their sleep position all night. What you can do is:

• Go to sleep on your side every time: when you go to bed, when you wake in the night and are going back to sleep, and for daytime naps
• Put a pillow behind your back to help stop you rolling all the way onto it
• If you wake up on your back, roll over and go back to sleep, no need to feel guilty

And daytime naps count too, especially when you nod off on the sofa or in a recliner in front of the TV.

How to arrange pillows so side sleeping is comfortable

Quick Answer: Several ordinary pillows work just as well as a pregnancy pillow: one under your bump, one between your knees, and one behind your back.

Try arranging them like this. Many moms say it makes a big difference:

1. A pillow between your knees keeps your hips and back from twisting and eases lower back pain
2. A flat pillow under your bump supports the weight of your growing belly
3. A long pillow or bolster (หมอนข้าง) behind your back stops you rolling onto it
4. If you already have a C- or U-shaped pregnancy pillow, that works too, but you don’t need to buy one. A few bolsters from around the house do the same job

But our hot weather is the real troublemaker, and snuggling up with lots of pillows makes it even hotter. Try thin cotton pillowcases and keep the room well ventilated, and you’ll fall asleep more easily.

Can’t sleep when pregnant? What can help

Quick Answer: Wind down before bed, cut back on caffeine in the afternoon, avoid long afternoon naps, and move gently during the day, for example with pregnancy yoga or swimming.

• Cut back on coffee, Thai tea and green tea after mid-afternoon, because caffeine makes it harder to fall asleep (read more in How much coffee can you drink a day when pregnant?)
• Do something relaxing before bed, like a warm shower, gentle stretching or listening to music
• Avoid long afternoon naps if you find it hard to sleep at night
• Gentle exercise suitable for pregnancy, if your doctor hasn’t told you not to

If you’re so itchy you can’t sleep, especially on the palms of your hands and soles of your feet, don’t ignore it. Read more in Itchy palms and soles in pregnancy: why doctors want to hear about it fast.

Call the hospital right away if…

Quick Answer: If you feel baby is moving less than usual, whether when you wake up or before bed, call the labor ward or the hospital where you get antenatal care right away, even in the middle of the night.

• Baby is moving less than their normal pattern. Don’t wait until morning, and don’t wait and see until your appointment (read How to count baby’s kicks)
• Don’t use a home fetal heart monitor to check instead of going to hospital, because it isn’t a reliable method
• A severe headache, blurred vision, or sudden swelling of the face, hands or feet (this may be pre-eclampsia)
• Regular, rhythmic contractions, your waters breaking, or bleeding

If you want to know what comes up in the other trimesters, go on to The trimester-by-trimester pregnancy guide.

To sum up in one line that’s easy to remember: after 28 weeks, go to sleep on your side, either side, and if you wake up on your back, just roll over. That’s all you need. We hope you sleep more comfortably tonight.