So is it best to sleep on the left or right? Is sleeping on your back ok?
The latest research says going to sleep on your side, any side, is safer than on your back, especially in late pregnancy (28 weeks on wards).
When lying on your back, the growing uterus and baby can compress major vessels (inferior vena cava and aorta) which move blood to and from the heart. This can reduce nutrient and oxygen flow to baby by up to 80% compared to when lying sideways, and has been found to be a major modifiable risk of late pregnancy stillbirth. There are definitely other contributing risk factors (such as a small-for-gestational-age baby, or maternal factor such as obesity), but the supine position (back) has been found to have an independent and additive correlation.
Of course, there is also the "left is best" recommendation which is the most effective position for blood flow (and therefore oxygen and nutrient flow) to baby.
So here are some tips:
Start sleep in a side lying position.
Use anything to get you comfy – a body pillow, or even a pregnancy sleep pillow (or a feeding pillow which can double up as the same!).
Other challenges like heartburn may also be improved with a more inclined lying position (even more pillow please).
If you wake up on your back, don't let this keep you up. The risks are higher for extended time spent on back, like falling asleep and staying there for several hours. When lying on your back for shorter duration, there are several adaptive responses in the baby, such as an increased heart rate. If you do find yourself on your back at 3am, just roll over and find a comfy position. ✌
Of course, if you have any other concerns about sleep positions, or any challenges with sleep, speak to your midwife or doctor.