Elara guides
Sleeping on your bump
Why “left side” advice exists — and how not to lose sleep over it.
Updated · Sources
Somewhere around the middle of pregnancy, sleep gets complicated. A growing bump, an active bladder and a busy mind all conspire against rest — and then someone tells you the position you've slept in your whole life is suddenly wrong. Here's what's actually behind the advice, and how to make peace with it.
The side-sleeping advice, explained
From the third trimester, guidance is to settle to sleep on your side rather than flat on your back. Lying on your back lets the heavy uterus press on a large vein (the vena cava) that returns blood to your heart, which can reduce blood flow and leave you dizzy. Side-sleeping keeps that vein clear. The left side is often mentioned because it slightly improves circulation, but either side is fine — the key is simply not flat on your back for the night.
What if you wake up on your back?
Don't panic. Your body has reflexes — if blood flow dips, you'll usually feel uncomfortable and shift without fully waking. The advice is about the position you settle into to sleep, not policing every minute. If you wake on your back, just roll to your side and drift off again.
Getting comfortable
- A pillow between your knees takes pressure off your hips and lower back.
- A pillow under the bump supports its weight so it doesn't pull you forward.
- A wedge behind your back lets you lean slightly without rolling fully flat.
- A full-length pregnancy pillow does all three at once if you want one object to hug.
The other sleep thieves
Position is only half the story. Heartburn eases if you avoid big meals late and prop your upper body up a little. Night-time bathroom trips shrink if you front-load fluids earlier in the day. Restless legs and cramps are common — gentle stretching before bed and staying hydrated help. And if your mind races, a wind-down routine without screens does more than any position ever will.
Why side-sleeping from 28 weeks
The NHS advises that the safest position to go to sleep in during the third trimester is on your side, either left or right. This applies to naps during the day as well as night-time sleep. Settling into your side at the start of sleep is what matters, because that is the position you are likely to spend the longest in.
Earlier in pregnancy you can sleep in whatever position is comfortable. Many people naturally move onto their side as the bump grows because lying flat becomes uncomfortable.
Tiredness is normal — to a point
Feeling tired is very common, especially in the first trimester and again in the last weeks. Hormonal changes, a growing bump, needing the toilet at night and worry all play a part. Resting when you can, going to bed earlier, accepting help and gentle regular exercise can make a difference.
Tiredness that feels extreme, or comes with breathlessness, a racing heart or feeling faint, is worth mentioning to your midwife or doctor, as it can have treatable causes such as anaemia.
A wind-down routine that helps
- Have your main meal earlier in the evening if heartburn wakes you, and raise your head and shoulders with an extra pillow.
- Drink plenty during the day and a little less in the last hour before bed.
- Keep the bedroom cool, dark and quiet, and put screens away before you turn in.
- Try gentle stretches for leg cramps and a warm bath or shower to relax.
- If worries keep you awake, write them down to raise at your next appointment.
Sleep and your baby’s movements
Many people notice their baby is active in the evening when they lie down. Getting to know this pattern is useful: if you notice your baby’s movements have slowed down, stopped or changed, do not go to sleep and wait until the morning — contact your maternity unit straight away.
Common questions
Is it safe to sleep on my back in the first trimester?
Yes. Before the third trimester you can sleep in whatever position is comfortable. The advice to go to sleep on your side applies from about 28 weeks.
Left side or right side — does it matter?
The NHS says either side is fine. What matters is going to sleep on your side rather than on your back in the third trimester.
What if I wake up on my back?
Do not worry. Roll onto your side and go back to sleep. The advice is about the position you settle into when you go to sleep.
Does the side-sleeping advice apply to naps?
Yes. In the third trimester, go to sleep on your side for daytime naps as well as at night.
Sources & editorial process
Written by the Elara editorial team from the sources above. This page has not been reviewed by an independent clinician. Read how we write and update health pages. Last updated .
Medical disclaimer: this page is general education, not medical advice, diagnosis or treatment. If you are worried about yourself or your baby, contact your midwife, doctor or maternity unit straight away. In an emergency call your local emergency number.