The Best Sleeping Position in Pregnancy
Why going to sleep on your side is advised from the third trimester, what to do if you wake up on your back, and how to make side sleeping comfortable.
Editorial draft: not yet reviewed by a clinician.
Go to sleep on your side from the third trimester onwards, and either side is fine. Tommy’s advises this because research has linked going to sleep on your back in the third trimester with an increased risk of stillbirth. The advice is about the position you fall asleep in, so waking up on your back is not a reason to panic. Just turn over.
Why the advice exists
The reasoning is mechanical. By the third trimester the weight of the uterus is substantial, and lying flat on your back places it over the major blood vessels that run along the spine, which can reduce blood flow. Research has linked going to sleep on the back in the third trimester with an increased risk of stillbirth, and that is the basis of the advice Tommy’s gives.
Two details in that sentence matter. It is about the third trimester, and it is about the position you go to sleep in, because that is the position you hold for the longest unbroken stretch.
From when, and what counts
- Before 28 weeks: sleep however is comfortable. Position is generally a comfort question rather than a safety one in the first two trimesters.
- From 28 weeks: settle on your side each time you go to sleep.
- Getting used to it early helps. Practising in the second trimester makes it feel normal sooner.
Waking on your back is not a failure
You cannot control what your body does at 4am, and nobody expects you to. Tommy’s makes the point plainly: if you wake on your back, turn onto your side and go back to sleep. There is no need to set an alarm, no need to lie awake guarding your position, and no need to feel you have done something wrong.
The only thing to avoid is deliberately settling on your back, and arranging pillows in a way that props you up on your back and keeps you pinned there.
Naps and the sofa count too
The advice covers any sleep, not just the night. Falling asleep on your back on the sofa in the afternoon is the most common way people end up back sleeping in the third trimester without ever deciding to, because a sofa nap is rarely planned. If you doze during the day, get onto your side before you drift off, and if you are in an armchair or a recliner, being tilted is preferable to being flat on your back.
Left or right?
Either. The advice is side, not left. You will read that the left side is preferable, usually on the grounds of blood flow, but the guidance you actually need to follow does not make you choose, and being able to swap sides is what makes a whole night possible without your hips seizing up.
Making side sleeping bearable
The advice is easy. Doing it for three months is not. What people commonly find helps:
- A firm pillow between the knees, to stop the top leg dragging the pelvis forward
- A pillow or rolled towel under the bump, so the weight is supported instead of pulling
- A pillow or wedge behind your back, which both stops you rolling flat and gives you something to lean against
- One good long pillow rather than an architecture of five, which tends to collapse by morning
- A slightly raised head end if heartburn wakes you
- Getting out of bed by rolling onto your side first, then pushing up, which is easier on the abdominal muscles
A dedicated pregnancy pillow works well for some people and is unnecessary for others. Ordinary pillows do the same job if you have enough of them.
The other reasons sleep is broken
Position is only one part of third-trimester sleep. Needing to urinate several times a night, heartburn, restless legs, leg cramps, breathlessness when lying down, vivid dreams and a baby who is most active the moment you lie still all contribute. None of those are signs that anything is wrong, and none of them are solved by trying harder.
Two things are worth raising with your midwife rather than tolerating: very loud snoring with pauses in your breathing, and sleep that has become impossible rather than merely bad. Both are things they would rather know about.
Do not sleep on these
Contact your midwife, maternity unit or doctor straight away, at any hour, if:
- Your baby’s movements slow down, change or stop.
- You have a severe or persistent headache, flashing lights or blurred vision, or sudden swelling of your face, hands or feet.
- You have sudden swelling, pain or redness in one leg, which is different from the general puffiness of late pregnancy.
- You have any vaginal bleeding, or your waters break.
- You have a fever or feel very unwell.
Waiting until morning because it is the middle of the night is the one thing not to do. Maternity units are staffed all night for exactly this.
Keeping track of how you are actually sleeping
PreBaby has a sleep log alongside the mood and symptom logs, so a run of bad nights is something you can show rather than something you try to describe from memory at an appointment. Seeing it written down also tends to make the practical fixes obvious, such as which nights heartburn was the problem and which nights it was the two trips to the bathroom.
Sources
This article is general information, not medical advice. Anything that worries you is a reason to contact your own midwife or doctor.
Questions and answers
What is the best position to sleep in during pregnancy?
On your side. Tommy's advises going to sleep on your side in the third trimester, and either side is fine, because research has linked going to sleep on your back in the third trimester with an increased risk of stillbirth. The advice is specifically about the position you fall asleep in, since that is the position you spend the longest time in. Before the third trimester, position is generally a matter of comfort rather than safety. Daytime naps count as sleep too, so the same advice applies to dozing on the sofa in the afternoon.
What should I do if I wake up on my back?
Simply turn onto your side and go back to sleep. Tommy's is clear that waking on your back is not a cause for alarm, because the advice concerns the position you go to sleep in rather than every position you pass through in the night. Your body will move while you sleep and you cannot control that, so there is nothing to feel guilty about. What is worth avoiding is deliberately settling on your back, or using pillows in a way that props you up on your back and keeps you there. If you keep waking on your back, a pillow or a wedge behind you can help.
Is the left side better than the right side?
Either side is fine. Tommy's advice is to go to sleep on your side, without specifying left or right, so you do not need to police which side you are on or feel you have got it wrong by settling on the right. You will hear the left side described as better, usually on the grounds of blood flow, but the practical guidance you need to follow is simply side rather than back. Being able to use both sides also matters for comfort, since hips and shoulders complain if you spend a whole night on one of them.
From what week should I start sleeping on my side?
The advice applies from the third trimester, which is usually counted from 28 weeks. Before then, sleep in whatever position is comfortable, although many people find their own habits change earlier than that as the bump grows and back sleeping stops being comfortable anyway. If you want to get used to it, practising side sleeping in the second trimester makes the switch easier, because a new sleep position takes a while to feel natural. If you have been given specific advice by your own midwife or doctor about position, follow theirs.
Sources
This is general information, not medical advice. It does not diagnose or treat, and it does not replace your own midwife or doctor. Anything that worries you is a reason to contact them.