Sleeping positions in pregnancy: what the evidence says

What the evidence actually shows

From around 28 weeks, going to sleep on your side is advised. Several studies have found an association between going to sleep on the back in the third trimester and a higher risk of stillbirth. The absolute risk remains low, and the advice is easy to follow, which is why it is given.

The mechanism: the weight of the uterus can compress the inferior vena cava and the aorta when you lie flat on your back, reducing blood return to the heart and blood flow to the placenta.

Left versus right: left has traditionally been recommended and the evidence for left over right is weak. Current guidance in most places is simply 'either side' — the important comparison is side versus back, not left versus right.

Before 28 weeks, sleep however you are comfortable. The advice applies to the third trimester.

And it is about the position you go to sleep in, because that is the position you spend most of the night in. It is not about policing yourself all night.

If you wake up on your back

Do not panic. Waking on your back happens to almost everyone and it is not evidence that harm has been done.

Simply turn back onto your side and go back to sleep. That is the entire correct response.

Many women wake because of the position — the body has its own protective response — which is part of why brief periods are not the concern.

A wedge or pillow behind your back makes rolling over less likely and is the practical fix if it happens repeatedly.

Do not lose sleep over sleep. Insomnia in late pregnancy is common enough without adding vigilance to it.

Getting comfortable

A pillow between the knees is the single most effective change, and it helps hip and pelvic pain as well as comfort.

A pillow under the bump supports the weight and reduces pulling on the back.

A pillow or wedge behind the back stops you rolling flat and gives something to lean against.

Propping the upper body helps heartburn and breathlessness, both common late on. Semi-reclined on your side is fine.

For hip pain, a softer surface under the hip or a mattress topper helps. For restless legs, ask your doctor about checking your iron and ferritin, which is a common and treatable cause in pregnancy.

You do not need a pregnancy pillow — ordinary pillows do the same job — and if you want one, our guide covers the shapes.

When to see a doctor

Go to the maternity unit the same day for: reduced or changed fetal movements, bleeding, severe or constant abdominal pain, leaking fluid, severe headache with visual changes, or sudden swelling of the face and hands.

See a doctor for: loud snoring, gasping or pauses in breathing during sleep — sleep apnoea in pregnancy is associated with high blood pressure and gestational diabetes and is treatable; severe insomnia; or severe restless legs.

Also for breathlessness that is new or severe, chest pain, or calf pain and swelling, which need urgent assessment.

This article is general information, not medical advice, and has not been reviewed by an obstetrician.

This article is general information, not medical advice, and is no substitute for personal medical advice. For any decision about your or your child's health, please consult your doctor.

Frequently asked questions

Q: I woke up on my back. Have I harmed the baby? — No. Turn onto your side and go back to sleep. The advice is about the position you fall asleep in.

Q: Is left definitely better than right? — The evidence for left over right is weak. Either side is fine; the meaningful difference is side rather than back.

Q: What about sleeping on my front? — Comfortable early on and impossible later. It is not dangerous; it simply stops being physically possible.

Q: Can I lie on my back for a scan or a massage? — Short periods on your back are generally fine, and tell the person if you feel dizzy or unwell, which is the signal to turn.