Sleeping on your side in pregnancy: why it matters from 28 weeks

From 28 weeks of pregnancy, the advice in Australia and the UK is to go to sleep on your side, for every sleep. That includes going to bed at night, daytime naps, and settling back to sleep after you wake in the night. Either side is fine, and if you wake up on your back, you haven't done anything wrong: just roll onto your side.

The reason is stillbirth. Australia's Safer Baby Bundle flyer says going to sleep on your side from 28 weeks halves the risk of stillbirth compared with going to sleep on your back. The NHS page on tiredness and sleep in pregnancy puts it the other way round: research suggests that after 28 weeks, falling asleep on your back can double the risk. Stillbirth after 28 weeks is uncommon, and side-sleeping is one simple thing within your control.

Why does sleep position matter after 28 weeks?

The Safer Baby Bundle, developed by Australia's Stillbirth Center of Research Excellence, says that after 28 weeks, lying on your back presses on major blood vessels. That can reduce blood flow to your womb and the oxygen supply to your baby. The NHS says the link "may be to do with the flow of blood and oxygen to the baby", and Australia's Pregnancy, Birth and Baby adds that it can also affect your baby's heart rate.

It helps to know what kind of evidence this is. NSW Health's information for maternity clinicians in Australia explains that the research comes from case-control and cross-sectional studies, which compared women who went to sleep on their back with women who went to sleep in other positions. It describes "an association" between going to sleep on your back and late stillbirth. In these studies the risk was 2.5 to 8 times higher, and a 2019 combined analysis found about 2.6 times the odds. NSW Health estimates that about 1 in 10 late stillbirths could potentially be avoided if women avoided going to sleep on their back.

To keep this in proportion:

• Stillbirth is uncommon. The Safer Baby Bundle flyer and Red Nose in Australia say stillbirth after 28 weeks affects about 1 in every 500 babies.
• Most causes aren't in your control. Pregnancy, Birth and Baby says stillbirth can happen for many different reasons, and most of them you can't change. Side-sleeping is one that you can.
• It's about how you fall asleep. The advice focuses on your going-to-sleep position, because that's the position you usually stay in longest.

The flyer notes that it was adapted from the Sleep On Side campaign by Tommy's, the UK pregnancy charity.

Which side should I sleep on, left or right?

Whichever is more comfortable. The Safer Baby Bundle says "either side is fine", the NHS says "either left or right", and Pregnancy, Birth and Baby says you can sleep on either or both sides. NSW Health's clinician page says going to sleep on the left or right side "appeared equally safe" in the research.

You may have heard that the left side is best. For stillbirth risk, the sources above don't favour one side. The left side does come up for a different reason: the NHS page on heartburn in pregnancy says sleeping on your left side can help with heartburn. And if you have pelvic pain, the RCOG leaflet on pelvic girdle pain suggests lying on the less painful side.

Swapping sides through the night is fine too.

What if I wake up on my back?

Don't panic. The Safer Baby Bundle says it's normal to change position during sleep, and many pregnant women wake up on their back. "That's OK!" Pregnancy, Birth and Baby explains that the position you fall asleep in is usually the one you're in for the longest, which is why the advice focuses on how you start each sleep.

What to do:

1. Roll onto your side as soon as you notice.
2. Settle back to sleep on your side, not on your back.
3. Don't set alarms to check. The sources don't ask you to wake yourself to check your position; the aim is to start each sleep on your side.

The Safer Baby Bundle adds that even if you find your back more comfortable, going to sleep on your back is not best for your baby after 28 weeks.

Does this apply to daytime naps?

Yes. Australia's Safer Baby website says to start every sleep lying on your side, both daytime naps and at night. Red Nose in Australia says side-sleeping applies to all sleeps, including naps and going back to sleep after waking. If you lie down for a rest and might drift off, lie on your side.

Naps can help with tiredness. Pregnancy, Birth and Baby suggests a daytime nap and resting when you can, and its sleep-habit tips suggest keeping naps to no more than 20 minutes. The NHS suggests not napping in the afternoon or evening, as it may mean you're not tired at bedtime.

How can I get comfortable sleeping on my side?

A growing bump can make lying down uncomfortable. These ideas come from the NHS, Pregnancy, Birth and Baby and the RCOG:

1. Bend your knees and put a pillow between them.
2. Support your bump with a pillow underneath it.
3. Try a pregnancy pillow if you like. Pregnancy, Birth and Baby says they come in many different shapes and sizes, but ordinary pillows work too.
4. Keep your knees together when you turn over if your pelvis hurts, as the RCOG suggests.
5. Wind down first. The NHS suggests relaxing before bed and avoiding tea, coffee or cola in the evening.

Some people also tuck a pillow behind their back. Use whatever helps you fall asleep on your side.

How can I ease heartburn, back pain and restless legs at night?

Heartburn

Heartburn is common in pregnancy and can keep you awake. Pregnancy, Birth and Baby says it happens as your growing baby presses on your organs. The NHS heartburn page suggests:

• not eating within 3 hours of going to bed
• eating small meals often, rather than 3 large meals a day
• cutting down on caffeine and on rich, spicy or fatty foods
• sitting up straight when you eat and just after eating
• propping your head and shoulders up in bed, so stomach acid doesn't come up while you sleep (you can still lie on your side)
• sleeping on your left side.

If that isn't enough, ask a pharmacist. The NHS says to tell them you're pregnant, as some antacids aren't suitable in pregnancy. See your midwife or doctor if changes to your diet don't help.

Heartburn that doesn't go away with heartburn medicines can be a sign of pre-eclampsia. The NHS pre-eclampsia page says this needs checking straight away, especially with a severe headache, vision problems, pain below your ribs, being sick, or sudden swelling of your face, hands or feet. Call your maternity unit.

Back pain and pelvic pain

The NHS back pain page suggests a mattress that supports you properly (a piece of hardboard under a soft mattress can firm it up), enough rest later in pregnancy, and a massage or warm bath. If the pain is bad, your doctor or midwife may refer you to an obstetric physiotherapist. Pregnancy, Birth and Baby says your back may ache more at night, and suggests taking breaks during the day and resting with your legs up.

For pelvic pain, the RCOG suggests a pillow under your bump and between your legs, and keeping your knees together when you turn over in bed. Tell your midwife or doctor, who can arrange a physiotherapy assessment. The RCOG says pelvic girdle pain is "not something you just have to 'put up with'".

Restless legs, cramps and other wakings

The NHS restless legs page lists pregnancy as a cause and says symptoms usually go away after giving birth. It's also linked to low iron, which a blood test can check. Things that may help include exercise during the day, regular bed and wake times, a warm bath before bed, and walking, stretching or massaging your legs when it starts. See your doctor if it's stopping you sleeping or affecting your mood. Check with your midwife, doctor or pharmacist before taking any medicine for it.

Leg cramps. Pregnancy, Birth and Baby says cramps are very common in pregnancy, especially at night. Stretch and massage your calf muscles when one starts.

Other things that wake you. Pregnancy, Birth and Baby suggests drinking well during the day and less before bed if you're up to pee. Tell your doctor or midwife if peeing burns or hurts, which could be an infection. It also says to speak to your doctor if you've started snoring during pregnancy.

What if my baby's movements seem different at bedtime?

If you notice a change in your baby's movements as you settle for the night, don't go to sleep and wait to see.

The NHS baby movements page says: "Do not wait until the next day – call immediately, even if it's the middle of the night." The RCOG movements leaflet says, "Never go to sleep ignoring a reduction or change in your baby's movements." For what's normal and what happens when you're checked, see baby movements in pregnancy.

When to get help

Call 911 now if you have back pain and lose feeling in one or both legs, your bottom or your genitals (NHS), or if you have heavy bleeding, a seizure or collapse. See signs of labor for other late-pregnancy emergencies.

Call your midwife or maternity unit now, day or night, if:

• your baby is moving less, has stopped moving, or their pattern has changed
• you have signs of pre-eclampsia: a severe headache, blurred vision or flashing lights, pain below your ribs, being sick, sudden swelling of your face, hands or feet, or heartburn that doesn't go away with heartburn medicines
• you have back pain with a fever, bleeding from your vagina, pain when you pee, or pain in your side under your ribs
• you have back pain in the second or third trimester that could be early labor (the NHS says to contact your doctor or midwife urgently).

Talk to your midwife or doctor if:

• poor sleep is worrying you or affecting your health
• you've started snoring
• heartburn, back pain, pelvic pain or restless legs aren't easing with the steps above.

The NHS says to speak to your doctor or midwife if sleeplessness comes with feeling hopeless or losing interest in things you used to enjoy, because treatment can help. If you have thoughts of harming yourself, call 988 (call or text) or 911 now.

What's useful to note down?

If sleep is a struggle, a few notes over a week can show your midwife or doctor the pattern: roughly when you wake, what woke you (heartburn, cramps, needing to pee, restless legs), and what helped. Note when your baby is usually busy, too, so a change is easier to spot. If movements change, call first and write it down later.