When is the right time to start using a pregnancy pillow?

Updated October 7, 2026.

Most pregnancy pillow advice tells you to start when sleep gets uncomfortable. That is a feeling, not a date. The sleep research does give a date. The clearest line is 28 weeks, when UK and Australian guidance says to go to sleep on your side. The American College of Obstetricians and Gynecologists (ACOG) points you to side sleeping from the second trimester. This page sets those dates side by side, so you can see the evidence behind each one and the pillow shape that suits each stage.

Short answer: Start when side sleeping stops feeling easy, and aim to be settled on your side by 28 weeks. ACOG says side sleeping may be best in the second and third trimesters (ACOG). NSW Health says to settle to sleep on your side from 28 weeks (NSW Health). That makes the second trimester the practical time for you to buy. That gives you time to practise. It is also late enough that the bump gives the pillow a job.

This guide is for: you if you are in the second trimester and deciding whether to buy a pregnancy pillow now, or past 28 weeks and still waking up on your back.

Key Takeaways

Three points to carry away: when the advice changes, how strong the evidence is, and which pillow shape suits the stage you are in.

1. The firm line is 28 weeks. A pooled analysis found 2.63 times the odds of stillbirth when women went to sleep on their back rather than their left side. The clinical summary reporting it advises you not to go to sleep on your back from 28 weeks (PubMed Central). UK and Australian advice starts at that week too.
2. US advice starts earlier and is softer. ACOG says side sleeping may be best for you in the second and third trimesters (ACOG). The Sleep Foundation says back sleeping may press on major blood vessels from around 20 weeks (Sleep Foundation). If you buy in the second trimester, you get weeks of practice before the third.
3. Health pages split 6, 5 and 1. We read 12 health pages on 27 September 2026. Six named 28 weeks as the start of side sleeping, 5 named an earlier week or the second trimester, and 1 named no week. Every page is listed in the count table below, so you can check each one.

On This Page

Eight questions, in the order most people ask them, from the week the advice changes to what to do when you wake up on your back.

What week does sleep position advice change?

US advice says side sleeping from the second trimester, while UK and Australian advice fixes the firm line at 28 weeks of pregnancy.

It depends on whose guidance you read. The gap is wider than most pillow pages admit. ACOG says side sleeping may be best in the second and third trimesters. It suggests you bend one or both knees, with a pillow between your knees and another under your belly (ACOG). The Sleep Foundation calls back sleeping generally safe in the first trimester. From around mid-pregnancy, it says, back sleeping may press on major blood vessels (Sleep Foundation).

Australian and UK advice comes later and is firmer. NSW Health says you should settle to sleep on your side from 28 weeks. That covers bedtime, going back to sleep after you wake, and daytime naps (NSW Health).

That leaves three dates. They build on each other rather than conflict: comfort decides early on, and the evidence takes over later. The table shows what a pillow does for you at each point.

Why does 28 weeks come up so often?

Studies of thousands of pregnancies linked going to sleep on your back after 28 weeks with about twice the risk of late stillbirth.

Because that is where the studies drew their line. Researchers asked women who had a late stillbirth how they went to sleep, and compared their answers with women whose pregnancies were ongoing. A pooled analysis combined data from hundreds of bereaved mothers and more than two thousand women with ongoing pregnancies. It put the raised risk at 2.6 times (University of Huddersfield). The NHS says it more simply. If you fall asleep on your back late in pregnancy, it says, you can double the risk of stillbirth (NHS).

The likely cause is the weight of the uterus pressing on a large vein. Late in pregnancy, when you lie on your back, the uterus can compress the inferior vena cava, the large vein that carries blood back to the heart. That reduces blood flow and oxygen to the baby (PLOS Digital Health via PMC). This is why the advice gets stronger as the bump gets heavier.

The risk itself is small. One habit change lowers it. A pillow makes the new habit easier for you to keep through the night. It does not change medical risk in any other way, and no study credits it with doing so.

Is the evidence on back sleeping settled?

Not fully. A large US study found no link before the final weeks, so the advice rests on late pregnancy and on how people fall asleep.

Not entirely, and the reason matters. The studies above asked women about their sleep after a loss had already happened. The authors of a large US analysis point out that asking about sleep position after the outcome leaves room for considerable recall bias (Obstetrics & Gynecology via PMC).

That US study asked women during pregnancy instead. It included thousands of women. It found no link between reported back or non-left sleeping and a combined measure of poor outcomes (Obstetrics & Gynecology via PMC). The catch is timing. Its last sleep questions came in mid-pregnancy, so it tells you little about the final weeks, which is when the earlier studies saw the effect.

A clinical summary draws the same line. It says current evidence shows your sleeping posture before 28 weeks does not affect pregnancy outcomes, and it advises you not to go to sleep on your back from that week (PubMed Central).

UK guideline writers looked at both kinds of study. An evidence review for the Royal College of Obstetricians and Gynaecologists still advised against going to sleep on the back in late pregnancy. It also noted that every study so far was retrospective (PLOS Digital Health via PMC).

What that means for you: before the third trimester, any position that brings you rest is fine. After it, side sleeping is the cautious default. A pillow helps you stay there.

Should you start before the bump makes you uncomfortable?

Yes, if you sleep on your back now. Starting in the second trimester gives weeks to learn side sleeping before late pregnancy.

For back and front sleepers, yes. Changing a lifelong sleep habit takes time, and the third trimester arrives either way. Pain is another reason. Nuffield Health estimates that between half and three quarters of pregnant women get lower back and pelvic pain (Nuffield Health). When you lie on your side without support, your top knee drops. That twists the pelvis.

The support ACOG describes is simple: a pillow between the knees and another under the belly, or a full-length body pillow (ACOG). That means you can test it for free. Try two bed pillows you already own for a week before you buy anything.

A small trial backs this up. In late pregnancy, a pillow built to stop back sleeping did no better than people's own pillows, with roughly an hour a night on the back either way (PubMed Central). If ordinary pillows keep sliding off the bed, a dedicated pillow earns its place.

If you already sleep on your side, you can take your time. Wait until the hips or lower back start to hurt, then buy. Our guide on what body pillow works for side sleepers covers how to set up support for knees and hips.

If you have a history of back trouble, you may want to start sooner. That is a call on comfort, not a medical decision. Nothing in the research argues against starting early.

Which pregnancy pillow shape fits which stage?

A wedge or straight body pillow covers the second trimester; a C or U shape earns its bed space once your belly and hips both need support.

Shape matters more than brand. The shape you need also changes over the months. A wedge supports one spot. A straight body pillow runs the length of the body and sits between the knees. C and U shapes add a section behind your back, which is what stops you rolling over. The cost is bulk. One review says these shapes are harder to handle and put space between partners, and that their covers are harder to refit (MemoryFoamMattress.org).

We found no trial comparing shapes, so the last two columns are our judgement, not a ranking.

For a longer comparison of the two big shapes, read is a U-shaped body pillow worth it, or will a long body pillow do?

How big is a full body pregnancy pillow compared with your bed?

The US listings we read put full body pregnancy pillows at well over four feet long and more than two and a half feet wide, so measure first.

They are bigger than they look in listing photos. A photo with no bed in it makes the scale hard to judge. Amazon and Walmart both sell PharMeDoc U shapes, and both listings put the length well over four feet (Amazon, Walmart). Two listings under one brand name can give different sizes, so go by the listing you are buying from. Narrower shapes exist too. Leachco's Half-Time model is listed at 22 inches wide (Amazon).

Width matters most once the pillow is on the bed. A C shape runs along one side of you. A U shape wraps around both sides. On a queen mattress, that can take up most of one person's half. Lay a tape measure across your side of the bed before you order. If you share a bed, a C or J shape leaves the other person more room.

Size also affects washing. A pillow this large may not fit a home washer. Check the care label for a removable cover before you buy, and plan on washing the cover rather than the whole pillow. Our pregnancy pillow buying guide covers fills and covers.

What do health pages say about when to start?

We read 12 health pages. Five named a week before 28 or the second trimester, six named 28 weeks, and one named no week at all.

We read 12 pages on 27 September 2026 from health bodies, clinics and health publishers. Each gives advice on sleep position or pillow timing in pregnancy. For each page we noted the earliest week it named, and we left out pages from pillow sellers. Six named 28 weeks, five named an earlier week or the second trimester, and one named no week. This is a count of what the pages say, and you can open each one from the table.

The split follows geography. It does not reflect disagreement about the science. Five of the six pages in that group come from UK or Australian organizations. The earlier group is mixed. It includes ACOG and a Scottish site. All twelve point you toward side sleeping; they differ only on when to begin. If your prenatal care follows ACOG, you will likely hear the earlier, softer wording.

What if you wake up on your back?

Roll back onto your side and go back to sleep. The advice is about the position you settle into, not every position you pass through.

Roll onto your side and go back to sleep. NSW Health says the position you fall asleep in is the one you hold longest. Waking on the back is no cause for worry, and either side appears equally safe (NSW Health). The NHS care bundle gives you the same instruction for naps and for waking in the night (ScienceDaily).

Rolling over is normal. Studies that recorded sleep position objectively found pregnant people spending from under a tenth to almost half of the night on their backs in the third trimester (PLOS Digital Health via PMC). Nobody holds one position all night, and the advice does not ask you to.

This is where pillow shape pays off. A straight pillow in front of you does nothing to stop a roll backward. A C or U shape puts a thick section behind the back, so turning over means rolling onto it. You may settle back onto a side before you fully wake. No source we read tested shapes against each other, so treat this as a practical nudge, not a proven fix.

If you keep waking flat on your back late in pregnancy, it is worth fixing. Tuck a folded pillow firmly along your spine. Mention it at your next prenatal visit as well, especially if you wake dizzy or short of breath.

Common questions

Short answers to the questions people ask most about timing, which side to lie on, first trimester use, and using the pillow after birth.

Can you use a pregnancy pillow in the first trimester?

Yes. Back sleeping is generally considered safe in the first trimester (Sleep Foundation), so a pillow at this stage is only for comfort. Sore hips are reason enough for you to start.

Is the left side better than the right side?

The early studies compared back sleeping with the left side. However, NSW Health says either side appears equally safe (NSW Health). Pick the side that helps you sleep better, and switch when one hip gets sore.

Does a pregnancy pillow stop you rolling onto your back?

A C or U shape makes it harder, because part of the pillow sits behind you. It won't make it impossible. The advice only covers the position people fall asleep in.

Do you need a pregnancy pillow at all?

No. ACOG suggests a pillow between the knees and one under the belly, or a full-length body pillow (ACOG). A small trial found that a pillow built to stop back sleeping did no better than ordinary pillows (PubMed Central).

Can you keep using a pregnancy pillow after the birth?

Nothing stops you. A C shape works well as a back rest for sitting up in bed. Wash the cover first after months of nightly use.

How do you wash a pregnancy pillow?

Check the care label before you buy. Many large pillows come with a removable cover, and the pillow itself may be too big for a home machine. If the label says to wash the cover only, a spare cover saves nights without one.