In the third trimester our advice is to go sleep on your side because research has shown that this is safer for baby. This includes night sleep and day time naps.
Can I sleep on my back during pregnancy?
Research has shown that in the third trimester (after 28 weeks of pregnancy) going to sleep on your back increases your risk of stillbirth. As the link has now been shown in 6 separate research trials, our advice is to go to sleep on your side in the third trimester because it is safer for your baby. The advice relates to any episode of sleep, including:
- going to sleep at night
- returning to sleep after any night wakenings
- day time naps.
We don’t want you to become anxious about this. If your pregnancy is uncomplicated your risk of stillbirth is low (1 in 200 babies are stillborn). Going to sleep on your side will make it even lower.
How reliable is the research?
The research linking going to sleep on your back to stillbirth is very reliable. Six case control research studies (in which information from women who have had a stillbirth is compared with information from women who have not) have been carried out into the woman or birthing person's sleep position and stillbirth and all have shown that there is a link.
What if I wake up on my back during the night?
The research has been focused on position going to sleep, not position during the night. If you wake up on your back, just settle back to sleep on your side.
We cannot control our position when we are asleep and a large bump is likely to be uncomfortable enough to prevent you from being on your back for long during the night. We also know that the position we go to sleep in is the position we spend the longest amount of time in during the night.
What could cause the increased risk of stillbirth?
Sleep position in the third trimester is important. If you are on your back the combined weight of baby and womb puts pressure on other organs in your body.
Researchers do not know for certain what exactly is causing the increased risk of stillbirth, but we already know the following, which could play a part :
- When sleeping/lying on your back the baby and womb put pressure on the main blood vessels that supply the uterus and this can restrict blood flow/oxygen to the baby and placenta.
- Other studies have shown that when a woman lies on her back in late pregnancy (compared to lying on side) the baby is less active and has changes in heart-rate patterns. This is thought to be due to lower oxygen levels in the baby when the woman or birthing person lies on their back.
Does it make a difference which side I sleep on in pregnancy?
There are many websites that tell you that the left side is best to sleep on during pregnancy. This is for the following reasons:
- One of the smaller research studies, from Auckland, New Zealand, showed that women who sleep on their left side on the last night of pregnancy halved their risk of stillbirth compared to those who slept on their right. However, the same finding has not been seen in any other trial (there have been three other published research studies since then).
- Sleeping on your left has been shown to help your kidneys to get rid of waste products and fluids from your body.
Therefore, while sleeping on your left side has not conclusively been shown to reduce your risk against sleeping on your right, there are reasons that you might choose to do so.
Tips for sleeping on your side in pregnancy
- Put pillows behind you to prevent falling on your back. It won’t prevent you being on your back for certain but is likely to make it more uncomfortable.
- If you have long hair, try tying it in a low bun, which may make it uncomfortable to sleep on your back for any length of time.
- If you wake up for any reason during the night, check your position and go back to sleep on your side.
- If you are likely to nap during the day pay the same attention to sleep position during the day as you would during the night.
Is it harmful to sleep on my stomach in pregnancy?
In the early days of pregnancy it is fine to sleep on your stomach. Your bump will not start showing until the second trimester and sleeping on your stomach is unlikely to be uncomfortable. In the third trimester, you will have a large bump and it is very unlikely that you would choose this position. However, if you do wake up on your stomach, don’t worry, just roll onto your side.
Sleeping on your side with Symphysis Pubis Dysfunction (SPD) / Pelvic Girdle Pain (PGP)
For women with SPD this can be very hard advice to follow. But the important thing is that you’re not lying flat on your back as this is what the research is related to.
If you can find a way to get comfortable on your side, for example with a pillow behind your back or in a V-shape, and perhaps one supporting your legs, then that would be ideal. What you want to do is to try to keep your legs level. If your top leg is dipping down on to your bottom leg, it is likely to cause pain, but if you keep them level using a pillow you might find it easier to sleep on your side.
However, there is a balance between sleeping in the safest position and getting as much good quality sleep as possible, which isn’t always easy in late pregnancy even without SPD/PGP.
We’d encourage you to seek a referral for physiotherapy if you’ve not done that already; speak to your midwife and they should be able to help with this.