Research has shown it's safer for your baby to sleep on your side in the third trimester.

The Midlands and North of England Stillbirth Study (MiNESS) found that women who go to sleep lying on their back have an increased risk of stillbirth compared with women who go to sleep on their side.  This includes daytime naps, going to sleep at night and going back to sleep after waking up in the night.

If your pregnancy is uncomplicated and your risk of stillbirth is low, going to sleep on your side will make it even lower.

How reliable is this research?

In shorty, highly reliable. Six separate case-control studies have all found a connection between sleep position and stillbirth.

What if I wake up on my back during the night?

Don't worry - if you wake up on your back, simply go back to sleep on your side. The position you fall asleep in is usually the position you spend the most time in during the night, and it's difficult to control your position while asleep.

Why the increased risk of stillbirth?

Lying on your back during pregnancy can cause the combined weight of the baby and womb to press on other organs.

Though researchers aren't certain about the exact cause of the increased risk, the following factors are believed to play a role:

  • When lying on your back, the baby and womb press on the main blood vessels that supply the uterus, potentially restricting blood flow and oxygen to the baby and placenta.
  • Other studies have shown that when a woman lies on her back late in pregnancy, the baby is less active and exhibits changes in heart rate patterns. This is thought to be due to lower oxygen levels when lying on the back.

Does it matter which side I sleep on? 

Many sources you'll come across online will suggest that sleeping on the left side is best during pregnancy. While sleeping on your left side has not been definitively shown to reduce your risk compared to sleeping on your right, there are a couple of reasons you might choose to sleep on your left:

  • A smaller study from Auckland, New Zealand, found that women who slept on their left side on the last night of pregnancy halved their risk of stillbirth compared to those who slept on their right. However, this finding has not been replicated in other studies (there have been three other published studies since then).
  • Sleeping on your left side helps your kidneys remove waste products and fluids from your body.

Tips for sleeping on your side during pregnancy:

  • Use pillows behind you to prevent rolling onto your back. This may not stop you from turning onto your back entirely but will make it more uncomfortable.
  • If you have long hair, tie it in a low bun to make it uncomfortable to sleep on your back for long.
  • If you wake up during the night, check your position and return to sleep on your side.
  • Pay attention to your sleep position during daytime naps, just as you would at night.

Is it harmful to sleep on my stomach during pregnancy?

In the early stages of pregnancy, it's fine to sleep on your stomach. In the third trimester, a large bump will make this position pretty uncomfortable. However, if you wake up on your stomach, simply roll onto your side.

Sleeping on your side with Symphysis Pubis Dysfunction (SPD) / Pelvic Girdle Pain (PGP)

If you have SPD, this advice can be difficult to follow. The crucial point is to avoid lying flat on your back, as the research pertains to this position.

If you can get comfortable on your side, using a pillow behind your back or in a V-shape and perhaps one between your legs to keep them level, this would be ideal. Keeping your legs level can reduce pain, whereas letting your top leg drop onto your bottom leg can increase discomfort.

Balancing the safest sleep position with getting good quality sleep can be challenging, especially in late pregnancy with SPD/PGP. If you haven't already, seek a referral for physiotherapy from your midwife. 

Baby Movements

Monitoring your baby’s movements is an important part of keeping track of their wellbeing, and has shown to be critical in preventing stillbirth. If you think your baby’s movements have slowed down or stopped, contact your maternity unit immediately. Midwives and doctors are there to help you - 24 hours a day, 7 days a week.

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