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truth about side lying sleeping in pregnancy

The truth about side-lying sleeping in pregnancy

Are you sleeping in a side-lying position?

So, I’m here to tell you the truth about side-lying sleeping in pregnancy. One of the most common questions pregnant women ask is about side-lying sleeping. Women are anxious about harming their babies by sleeping in any other position that is not side-lying. The result? Tired and anxious mums-to-be who can’t get comfortable on their sides. So I thought I share the research behind the Sleeping On Your Side campaign.

There were three studies published in 2011, 2015 and 2017, and all were done in Australia or New Zealand. There was a link found between women going to sleep on their back and stillbirth occurrences. The 2015 study found that sleeping on your back would be an added risk factor to an already unwell baby. Of those 103 women who had a stillbirth – 9.7% slept on their backs.

An English study recently published (2017) looked at a larger group of stillbirth cases (291 cases). They found that mums who had a stillbirth were 2.3 times more likely to sleep on their backs.

To put it into context, research shows that mums who had a stillbirth were 1.9 times more likely to smoke during pregnancy. So the authors of the paper argue that sleeping on your back has a more powerful effect than smoking does.

Stillbirth rates in England in 2016 was 4.3 per 1000 total births or 0.43% (Office for National Statistics). We must remember that this is extremely low rate and that half of stillbirths (0.22%) are still unexplained, with the remainder resulting from lack of oxygen or trauma just before or during birth (0.11%), congenital anomalies (0.05%) or infections (<0.04%).

It seems this campaign has made a lot of pregnant women anxious because they had not known this or that they found it difficult or uncomfortable to sleep on their left side and consequently worried that they were harming their babies.

Why does side lying sleeping in pregnancy help my baby?
So, a little background physiology is necessary here to understand the rationale. A heavy uterus and baby can compress the vena cava which is a major blood vessel that takes blood back to the heart to be pumped to the lungs for oxygenation. This restricts the blood flow to and from the lungs and thereby reduces both your and your baby’s oxygen level.

When does the weight of the uterus and baby become an issue? This is where perhaps you might find different opinions. Some literature, advise you to start sleeping on your side from 16 weeks or after the first trimester. However, I find this too restrictive. Many women are barely showing at this stage and therefore the uterus won’t be causing any issue. This is why during the relaxation part of my yoga classes, I ask you to rest on your side after approx 30 weeks of pregnancy.

Prior to ~30 weeks is still fine to be lying flat on your back (unless you are carrying twins!). However, this is a rough guide – as every pregnancy is different. If you feel faint or breathless earlier than 30 weeks then avoid lying completely on your back. Remember, it is how heavy your uterus feels.

What if I have woken up and found myself on my back?
Remember that these studies focus on the position you go to sleep in, which is the one you will spend most of your time in. If you do wake up on your back, it’s OK. Just turn over again onto your side and settle back to sleep. The fact that you’re waking up on your back probably means that you were probably uncomfortable, so it’s unlikely you have been in that position for long.

Does it have to be on my left side?
No, the truth about side lying sleeping in pregnancy is that you can also lie on your right side. The 2015 study found that there was no significant difference between sleeping on your left or right side. When I was working as a midwife in labour ward, we often used the CTG machines for continuous monitoring. When baby’s heart rate dipped, one of the first things we do, is get the woman to lie on her left side and that usually helps the heart rate to get back to normal. However, sometimes it didn’t help, so we asked the woman to lie on her right side and this did the trick. Just shows that every baby can have different preferences!

What if I can’t get comfortable on my side? 
In labour, midwives recommends that women lie at a tilt of at least 30 degrees to ensure babies are not lying on the vena cava, so that may be a solution if lying on the side is painful/uncomfortable. Also, using pregnancy pillows to support your legs and back can help. The main thing is that you do not lie completely flat on your back. If you do wake up on your back and feel breathless or faint then change position.


👉🏻 The take home message is – as long as you start off by going to sleep in a side-lying position and turning back over if you wake up on your back, then you are doing everything you can to reduce your risk 👈🏻 


I’m easing my way out of maternity leave and starting to teach pregnancy yoga classes in person again at Yoga West. For the end relaxation part of the class, we will be lying on our sides. Please ensure you bring a cushion to rest your top leg on when side-lying, and a blanket to cover yourself! Head to CLASSES for my timetable.