Sleeping positions in pregnancy, trimester by trimester
Left and right are equally fine. The one position to avoid going to sleep in, from 28 weeks, is flat on your back.
Updated October 13, 2026 · sources checked October 13, 2026
In short
From 28 weeks, go to sleep on your side, left or right. The NHS says research links falling asleep on your back after 28 weeks to about double the risk of stillbirth, and a large analysis found the left and right sides equally safe. If you wake up on your back, simply turn onto your side. Earlier in pregnancy, sleep in whatever position is comfortable.
The rule that matters: side-sleeping from 28 weeks
The NHS puts it simply: the safest position to go to sleep in is on your side, left or right. Research suggests that after 28 weeks, falling asleep on your back can double the risk of stillbirth, possibly because of the flow of blood and oxygen to the baby.
ACOG explains the mechanism in plain words: when you lie on your back, your uterus presses on a large vein that returns blood to the heart, which can briefly lower your blood pressure. That is also why you may feel dizzy lying flat on your back later in pregnancy.
What counts is the position you fall asleep in, at night and for daytime naps. Waking up on your back happens to everyone; turn over and go back to sleep.
Is this normal? When to call
Waking up on your back is normal and is not something you did wrong: just turn onto your side. Broken sleep and night-time loo trips are common later in pregnancy. Call your midwife or maternity unit straight away, day or night, if your baby's usual pattern of movements changes. For urgent advice in the UK, NHS 111; in an emergency, 911 (US) or 999 (UK).
What the research shows
| Study | Who | What it found |
|---|---|---|
| Cronin et al., 2019, meta-analysis of 5 case-control studies | 851 late stillbirths, 2,257 ongoing pregnancies, from 28 weeks | Going to sleep on the back: adjusted odds ratio 2.63 compared with the left side. Right side similar to left (1.04) |
| Silver et al., 2019, US nuMoM2b cohort | 8,706 first-time mothers, sleep assessed up to 30 weeks | No link between back or right-side sleep and stillbirth, small babies or high blood pressure up to 30 weeks |
Read together, the two studies explain why the advice starts at 28 weeks and not before: the association is seen in late pregnancy. The authors of the meta-analysis estimated that if every woman from 28 weeks settled to sleep on her side, late stillbirths could fall by about 5.8%.
Position by trimester
| Stage | What is fine | Comfort tip |
|---|---|---|
| First trimester | Any position, including back and front | Sleep in whatever position feels comfortable |
| Second trimester, up to 27 weeks | Any comfortable position; a good time to practise side-sleeping | Start using a pillow between your knees |
| Third trimester (28 weeks to birth) | Go to sleep on your left or right side | Pillow behind your back, under the bump and between the knees |
Building a comfortable side-sleeping nest
ACOG suggests sleeping on your side with one or both knees bent, a pillow between your knees and another under your belly, or a full-length body pillow. In practice:
- Lie on your side with your knees and hips slightly bent.
- Put a pillow between your knees and ankles so your top leg does not pull your pelvis forward.
- Slide a small pillow or wedge under your bump.
- Place a pillow lengthways behind your back so you do not roll onto it.
- If heartburn wakes you, raise your head and shoulders with an extra pillow.
A pregnancy pillow combines these supports in one piece; ordinary pillows work too.
Printable checklist: tonight's side-sleeping set-up
For your partner
If you share the bed, a long pillow behind her back takes up some of your space and is worth it. If you notice she has rolled onto her back late in pregnancy, a gentle nudge is enough: there is no need to wake her in a panic, as what matters is the position she falls asleep in.
Sleeping better when your bump gets in the way
- Avoid tea, coffee or cola in the evening: the NHS notes caffeine can make it harder to fall asleep.
- Turning over in bed hurts with pelvic girdle pain: keep your knees together as you roll, and talk to your midwife about a physiotherapy referral (see back pain and sciatica in pregnancy).
- Night-time trips to the loo are normal later in pregnancy; a dim night light makes getting back to sleep easier.
When to call your midwife or doctor: the full list
- Any change in your baby's usual pattern of movements: the NHS says to call your midwife or maternity unit immediately, day or night, and not wait until the next day.
- Dizziness, faintness or feeling unwell when lying down that does not ease when you turn onto your side.
- Sleeplessness together with low mood or loss of interest in things you used to enjoy, which the NHS notes can be a sign of depression.
- Emergencies: 911 in the US, 999 in the UK. For urgent advice in the UK, NHS 111.
Questions parents ask
Is it better to sleep on my left or my right side?
Either. The NHS says the safest position is on your side, left or right, and the 2019 analysis of five studies found similar odds for both sides. Pick the side you find comfortable and switch whenever you like.
What if I wake up on my back?
Do not worry. The NHS advice is about the position you fall asleep in: turn onto your side and go back to sleep. A pillow behind your back makes rolling over less likely.
Can I sleep on my stomach while pregnant?
Early on, if it is comfortable. As your bump grows, lying on your front becomes impractical for most women, and side-sleeping becomes the natural choice.
Can I sleep on my back in the first trimester?
Yes. The side-sleeping advice applies from 28 weeks. A large US study following women through 30 weeks found no link between back-sleeping and stillbirth before that point.
Sources
- NHS — Tiredness and sleep problems in pregnancy checked October 13, 2026
- NHS — Preventing stillbirth (going to sleep on your side) checked October 13, 2026
- ACOG — Exercise During Pregnancy (lying flat on your back) checked October 13, 2026
- ACOG — Back Pain During Pregnancy checked October 13, 2026
- Cronin RS et al. (2019), EClinicalMedicine — Going-to-sleep position and late stillbirth, IPD meta-analysis (PMID 31193832) checked October 13, 2026
- Silver RM et al. (2019), Obstetrics & Gynecology — Maternal sleep position through 30 weeks, nuMoM2b cohort (PMID 31503146) checked October 13, 2026
Mamavela explains; it does not replace your midwife, doctor or pediatrician, who know your situation. If something worries you, call them. In an emergency, call 911 (US), 999 (UK) or 112.