If you are pregnant and lying awake at 2am trying to work out whether you are on the correct side, or panicking because you woke up on your back, this one is for you.

Sleep during pregnancy is hard enough without the anxiety of wondering if you are doing it wrong. Between the back pain, the heartburn, the trips to the bathroom and a baby who seems to be most active the moment you lie down, getting a decent night’s sleep can feel impossible. And then there is the conflicting advice about which position is safe.

I want to clear this up, because a lot of the guidance out there is outdated or oversimplified, and it is causing unnecessary stress.

Do you have to sleep on your left side?

No. This is probably the most common piece of pregnancy sleep advice, and it is not quite right.

The old recommendation was based on the anatomy of the inferior vena cava (the large vein that returns blood from your lower body to your heart), which sits slightly to the right of your spine. The theory was that lying on your left would take pressure off this vein and improve blood flow to the placenta. It made sense anatomically, but the research does not support it as a strict rule.

A large individual participant data meta-analysis by Cronin and colleagues (2019), pooling data from five studies (851 stillbirths and 2,257 controls), found no difference in risk between going to sleep on your left side and going to sleep on your right. The adjusted odds ratio was 1.04, which is statistically no different at all.

Either side is safe. Whichever side is more comfortable for you is the right one.

When does sleeping on your back become a concern?

In early and mid-pregnancy, you do not need to worry about your sleep position at all. A large prospective study of over 8,700 women (Silver et al., 2019) found no association between sleep position before 30 weeks and any adverse outcomes. Sleep however you are comfortable.

From around 28 weeks, the current recommendation is to go to sleep on your side. This is based on several large studies (Cronin et al., 2019; Heazell et al., 2018) which found that settling to sleep on your side in the third trimester is a simple, protective measure. It is what led to the Tommy’s “Sleep On Side” campaign in the UK.

The reason is straightforward. As your uterus gets heavier in the third trimester, lying flat on your back for extended periods can reduce blood flow through the large vessels behind the uterus. Going to sleep on your side avoids this. Most women in late pregnancy find lying on their back uncomfortable anyway, so your body is already guiding you in the right direction.

What if you wake up on your back?

This is the question I get asked most, and I want to be really clear: it is fine. Just roll onto your side and go back to sleep.

The research looked at “going-to-sleep position,” the position you settle into when you fall asleep. It did not measure every position you move into during the night, because you cannot control that. Everyone shifts during sleep, and that is completely normal.

Your body is generally quite good at guiding you here. Most women in late pregnancy find lying on their back uncomfortable before they even fall asleep, which is your body doing exactly what it should.

Why sleep gets so difficult in the third trimester

Nearly half of all pregnant women experience clinically poor sleep quality, and it gets significantly worse as pregnancy progresses (Sedov et al., 2018). By the third trimester, the average sleep quality score is well above the clinical threshold for a sleep problem.

There are several reasons for this:

Back and pelvic pain. Low back pain affects around 40% of pregnant women, rising to nearly 48% in the third trimester (Salari et al., 2023). More than half of those women report that pain disturbs their sleep. Pelvic girdle pain makes it especially difficult to turn over or find a comfortable position.
Frequent urination. Your bladder is under pressure from the growing uterus, and blood volume changes increase kidney output at night.
Heartburn and reflux. Hormonal changes relax the lower oesophageal sphincter, and the upward pressure from the uterus makes it worse when lying flat.
Restless legs and cramps. Both are more common in pregnancy and tend to be worse at night.
Anxiety. About the birth, about the baby, about sleep itself. It all adds up.

Why sleep quality matters

Good sleep during pregnancy is not a luxury. A large systematic review by Lu and colleagues (2021) found that better sleep quality is associated with better outcomes for both mum and baby. The encouraging part is that sleep is something you can actively improve. Small changes to your setup, your routine and how you manage pain at night can make a real difference to how you feel during the day and how well your body handles the demands of pregnancy.

What actually helps

Get your pillow setup right

A pregnancy pillow or a simple arrangement of regular pillows can make a real difference. A randomised controlled trial by Feldthusen and colleagues (2021) found that pregnant women with pelvic girdle pain who used supportive pillows and a memory-foam mattress had significantly lower pain at night and gained an additional 26 minutes of sleep per night compared to the control group.

You do not need an expensive pregnancy pillow if it is not in the budget. A regular pillow between your knees takes the rotational strain off your pelvis and lower back. Another behind your back can stop you rolling onto it during sleep. A thin pillow or folded towel under your bump can support its weight when you are on your side.

Address the pain

If back pain or pelvic pain is keeping you awake, it is worth getting it assessed rather than just enduring it. Pregnancy-related musculoskeletal pain responds well to treatment, and getting on top of it improves both your days and your nights. Chiropractic care during pregnancy is gentle and adapted for your changing body. We use specific positioning and techniques that are comfortable and safe at every stage.

Elevate your upper body slightly

If heartburn is waking you up, sleeping with your upper body slightly elevated (an extra pillow or a wedge under the mattress) can reduce reflux. Avoiding large meals close to bedtime helps too.

Keep a consistent routine

Your body clock matters. Going to bed and waking at roughly the same time, limiting screen time before bed and keeping the room cool and dark all support better sleep. These seem basic, but they make more difference than most people expect, especially when your sleep is already fragmented.

Move during the day

Regular exercise during pregnancy improves sleep quality. Even a daily walk can help. If you are unsure about what exercise is safe, our guide to postpartum exercise covers the principles, and we also see pregnant women in practice for exercise guidance and pregnancy-related pain.

The simple version

Before 28 weeks: sleep however you are comfortable. Position does not matter.
From 28 weeks: go to sleep on your side. Either side is fine.
If you wake on your back: just roll over. Do not stress about it.
If pain is keeping you awake: get it looked at. It is treatable.

Sleep is hard enough in pregnancy without adding guilt or anxiety on top. Be kind to yourself, set up your pillows, lie on whichever side feels right and know that you are doing just fine.

If pregnancy-related pain is affecting your sleep and you would like some help, get in touch or book an appointment.

References

SLEEP POSITIONS DURING PREGNANCY: WHAT THE EVIDENCE ACTUALLY SAYS