Q: Is it true that it’s only safe to sleep on my left side while pregnant? I can’t get comfortable and am exhausted. What should I do?
A: The short answer is, No! As a midwife it’s so sad to hear how much this misinformation is spread through the pregnant population. This is contributing to a lack of sleep in many pregnant people. Let’s be honest, you’re pregnant, getting a good night sleep is probably not going to be as easy as it used to be, for several reasons. At the start of pregnancy hormones can impact our ability to get decent sleep. As pregnancy continues, our poor bladder gets crushed by our growing uterus and we’re up every few hours (or minutes it seems!) to pee. Eventually comfortable positions become harder and harder to come by, and getting enough hours of decent sleep can be really tough.
As your pregnancy progresses it’s very common to begin to receive advice from friends, family and health care providers about safe sleep positions and specifically about sticking to a left lying position. “SOS” or Sleep on Your Side has even been coined as a term, and is promoted by many websites, but is this advice warranted?
The theory behind the risk of sleeping on your back is that the pressure of the growing uterus can compress the abdominal aorta & inferior vena cava in the pregnant person (known as aortocaval compression syndrome). In non-scientific jargon, this means that your major blood vessels can get pinched off, reducing blood flow through them, possibly causing a drop in blood pressure, which in turn could cause a drop in oxygen going through the placenta to baby. This sounds terrifying and often leads to pregnant people not sleeping well because they’re scared of changing sleep positions and ending up on their back during the night. Instead of fear mongering poor expectant people out of sleep, let’s talk about what the science says.
In recent years a few small studies (one from Ghana & one from New Zealand) have looked at stillbirth and sleep positions. Both concluded that any sleep position except left lying increased the risk of late stillbirth. The problem with these studies is that they are relatively small retrospective studies. This means that instead of studying something going forward, they relied on interviews with the pregnant person after the loss to compile their results. Asking someone to recall their sleep position after they have lost their baby is not necessarily the best way to study the topic. It’s possible that participant’s recall might be distorted by what recently occurred. I know I wouldn’t be able to confidently cite my sleep position if I had recently experienced such a tragic loss. These studies definitely highlight the need for more research, but don’t provide us with strong enough evidence to make clinical recommendations.
In comparison to these retrospective studies, controlled studies that assessed the impact of sleep position on maternal or fetal well being through measurable values such as oxygen levels, heart rate and blood pressure, did not agree. One of the papers I love to site on this topic was complied right here in Toronto at Mount Sinai Hospital by Dr Farine & Dr Seaward, two highly respected Obstetricians I have had the pleasure of working with. Their analysis of the available studies showed that in the small percentage of people who experience symptoms of compression (eg. dizziness, sweating, nausea, shortness of breath) from laying on their back, only 2-4% of these pregnant people actually experienced any aortocaval compression and that “Even in this small minority of symptomatic women, there is no evidence of fetal compromise”1 Their analysis found that most people who do experience a drop in their blood pressure will automatically shift their sleep position, because their body does not like how it feels. I personally experienced this in my pregnancies. In my first two pregnancies I could sleep on my back comfortably with no issue. However, in my last pregnancy, I immediately started to feel unwell when flat on my back, so I naturally changed positions or used pillows to wedge myself up a bit. It’s always important to follow your body and change positions as necessary.
As a Registered Midwife I believe very firmly in Informed Choice. Discussing these findings with clients, instead of creating a blanket statement to avoid any position except SOS, is essential. We need to remember that by placing the sole responsibility of survival of the baby on the pregnant person we are laying blame if stillbirth occurs. No one should ever feel like they are to blame for something that we truly do not understand. I always remind my clients that we all assess risk differently, so if you feel safer sleeping on your left side than that is ok, but please don’t let these small studies keep you from getting the sleep you need at such an exhausting time. In addition, if you have a high-risk pregnancy there might be indications for a certain sleep position to be used. So make sure to engage in a discussion with your health care provider surrounding the reasons for their various recommendations.
Carolyn Sinclair is a registered Midwife, heart & stroke foundation instructor, baby-wearing educator and mom of three. She regularly teaches group classes including: prenatal classes, parent-prep Classes, baby wearing workshops, CPR workshops, starting solids workshops and also offers many private services including registry support and in home classes. You can find out more on Carolyn’s website With Care