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You will spend about one third of your life sleeping. Sleep is so vital to your health and the health of your baby. Especially early and later in your pregnancy when you are more prone to fatigue, you will be spending a lot of hours sleeping. The big question is whether there is an ideal position to be sleeping in. In recent years there have been studies making headlines that sleeping on your back is dangerous for you and your baby. This has led to many expecting mothers waking up on their backs and panicking. I want to keep you from having to experience that. This article digs into the pros and cons of different sleeping positions, examines the research on which position is ideal, and digs into the statistics on your risks.

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Sleep During Pregnancy

A study of pregnant mothers looked at sleep quality and disturbances. 76% reported poor sleep quality. 79% reported difficulty finding a comfortable position. All 2,427 participants reported waking up frequently. There are a lot of issues that can impact your sleep during pregnancy. Finding a comfortable position is key to sleeping well. As your body goes through changes during your pregnancy the positions that are comfortable, and how your support your body in those positions, may need to change.

The Basic Sleeping Positions

There are three basic positions to sleep in. These are on your back, on your stomach, and on your side.

Sleeping on Your Stomach

Sleeping on your stomach, or in the prone position, is not ideal for your spine. For that reason, if you are having any issues with your back or neck you should not be sleeping on your stomach. This is true whether or not you are pregnant. Back pain tends to be more common later in pregnancy when it is unlikely you would be sleeping on your stomach.

If you are pregnant and normally sleep on your stomach, enjoy it while you can. You may be okay continuing to sleep on your stomach through your first trimester. As your belly grows you will not be able to maintain this position. For this reason, you may want to consider trying to make it a habit of sleeping in another position now. On the other hand, sleep can be challenging at times when you are pregnant and if it works for you now, great. You can always adjust later as needed.

Sleeping on Your Back

Sleeping on your back is sometimes referred to as a supine position. There are some pros to this position. The biggest is that it is a good position for your spine. In the long term it may be better for your face to not have your skin smooshed up against a pillow. If you have heartburn sleeping on your back propped up may be helpful. A big downside of this position is that it can make sleep apnea or snoring worse.

When you are pregnant you have some additional considerations for sleeping on your back. As your uterus grows more pressure is put on your intestines and your vena cava. Your vena cava is the main artery that carries unoxygenated blood from the lower half of your body back to your heart. If there is a lot of pressure on this vein it could decrease the flow of blood which will ultimately decrease your oxygen and oxygen getting to your baby. Additional pressure on your intestines means that you could make digestion less efficient. It is generally recommended that you avoid sleeping on your back in the 2nd and 3rd trimesters. We will dig into the research on the risks of sleeping on your back later in this article.

Side sleeping

The majority of people sleep on their side. There are a lot of variations of this position depending on how your arms and legs are positioned. The biggest pro of sleeping on your side is that it maximizes blood flow. Some downsides are pain in your shoulders, hips, or your back if your spine is not aligned properly when you sleep. If you are having pain in your hips during your pregnancy it could make sleeping on your side challenging, or you may need to switch sides often.

Left vs. Right Side

If you have to pick a side, your left side is ideal. This is true whether or not you are pregnant. The reason the left side is preferred is that it promotes blood flow and digestion. Your vena cava is located to the right of your spine. Sleeping on the left side puts less pressure on this vein. This means the deoxygenated blood from the lower half of your body can flow easier to your heart to be replenished with oxygen. When you are pregnant, this also means your baby has access to more oxygen. Due to the location of your digestive organs, it may also improve digestion to sleep on your left side over your right.

The Research

Sleep Position and Adverse Pregnancy Outcomes

A large study looked at sleep position and adverse pregnancy outcomes. The outcomes examined included stillbirth, small for gestational age babies, and gestational hypertensive disorders. Hypertension is high blood pressure and those disorders include preeclampsia and eclampsia. Remember that blood flow can be impacted with additional pressure on the vena cava. It is important to note that this study looked at these outcomes and sleep positions up through week 30 of pregnancy, so they did not get too far into the third trimester. The good news is that they found no association between sleep position the night or the week before the study visit with adverse pregnancy outcomes prior to 30 weeks. It is also worth noting that women with adverse outcomes had higher BMIs, were more likely to smoke, more likely to have chronic hypertension, pre-gestational diabetes, and kidney disease.

Recall Bias

This study looked at the sleep position prior to the occurrence of the pregnancy outcome. The researchers note the other studies on this topic have the potential for recall bias, perhaps linked to parental guilt. Most of the research on this topic relies on surveys about participants’ sleep. To participate in the study, they must recall details about their past sleep habits. Recall bias happens when participants in a study are systematically more or less likely to recall and relate information based on their outcome. Someone who experienced a stillbirth (in the case group) may search their memory deeper for connections of how their actions could have affected their baby, more than someone who did not have that experience (in the control group).

Still Birth and Sleep Position

A stillbirth is defined as the birth of a baby who died in utero after 28 weeks. Prior to 28 weeks, it is considered a miscarriage. I have to acknowledge that stillbirth is a heartbreaking tragedy. I know the possibility of that happening is terrifying. My aim is not to freak you out and not to be insensitive about the heartbreak of stillbirth. I want to give you the facts and research about this so you can be educated. Especially when you may be seeing news headlines about how your sleep position may impact your risk for stillbirth.

Modifying Sleep Position as an Intervention

Sleep position as an intervention to limit stillborn risk is very attractive because it is an inexpensive and easy intervention. There is some association between sleep-disordered breathing and adverse outcomes like hypertension, small for gestational age, both of which are associated with stillbirth. There is also a link between higher stillborn risk and maternal obesity. Maternal obesity is also associated with an increased risk for sleep-disordered breathing and sleep apnea, which is worse when you sleep on your back. This seems like an endless loop and it is acknowledged in nearly every study examined in this article that there is a link between sleeping on your back and sleep-disordered breathing because sleeping in a supine position exacerbates sleep-disordered breathing.

The Evidence on Sleep Position and Stillbirth Risk

A New Zealand study included 155 women who had a stillbirth and they looked at sleep position at the time of going to sleep and on waking. This was compared to a control group of 305 women. The researchers found that women who slept on their back or on their right side on the previous night (before stillbirth or interview) were more likely to experience a late stillbirth compared with women who slept on their left side. The absolute risk of late stillbirth for women who went to sleep on their left was 1.96/1000 and was 3.93/1000 for women who did not go to sleep on their left.

A study in Australia looked at potentially modifiable risk factors for late pregnancy stillbirth. This included a total of 103 women in the case group who had a stillbirth and a control group of 192 women. Sleep position was based on a question focused on the participant’s usual sleep position over the past month. They compared the supine position to all other sleeping positions and found that sleeping on your back has a higher risk of stillbirth. This conclusion was reached when comparing the 9.7% of women who experienced stillbirth reported usually sleeping on their backs compared to 2.1% of women in the control group. The researchers state that sleeping on your back may be an additional risk for a vulnerable fetus. They support the hypothesis that there is a triple risk for stillbirth. Those three risks are maternal risk factors, fetal risk factors, and a stressor, which they say could be compression of the vena cava due to sleeping on your back. A takeaway from this study is that it is unlikely sleeping on your back is the sole cause of a stillbirth.

One study also examined a possible link between sleeping on your back and stillbirth. In this study, the number of women who reported sleeping exclusively on their back was small, they grouped those who reported sleeping on their back and side in the case group of back sleepers. Of the 19 participants that reported sleeping on their backs 3 had a stillbirth, compared to 6 stillbirths in the group of 197 who reported sleeping in other positions. The researchers relate sleeping on your back as a contributor to low birth weight and subsequently stillbirth. The postulate that because of this causal relationship stillbirths might be prevented by changing maternal sleep position. Keep in mind that the rate of stillbirth in the population in Ghana is much higher than in many other countries.

A clinical trial in the UK looked specifically at the odds of late stillbirth associated with self‐reported maternal going‐to‐sleep position on the night prior to stillbirth. This study included over a thousand participants with 291 in the case group who had a stillbirth and 733 in the control group. They found that women who had a late stillbirth were 2.3 times more likely to report going to sleep on their backs the night prior to the stillbirth. 

I know the summaries of these studies have a lot of numbers. Let’s put this all into perspective.

Limitations of the Research

All of the studies done rely on self-reported data. The participants report the quantity and quality of their sleep, along with self-reporting the positions they slept in. A small study was done to examine some really interesting questions about the accuracy of self-reported sleep positions and how realistic it is to get expecting mothers to sleep on their left side. This study involved thirty women in late pregnancy who spent three nights sleeping under observation. The participants were instructed to settle to sleep on their left side and if they woke overnight to settle back to sleep on their left. On average, women accurately reported the time spent sleeping on their left side. Some of the individual differences were as big as 3.5 hours. A lot of research relies on self-reported data, but there is a downside to this because we are not always accurate in our recollection and reporting.

The second question addressed in this study was what happens to the sleep position and sleep time of women in late pregnancy when they are instructed to try to sleep on their left side? The result was that around 60% of participants spent the night in this position. Again, we are looking at averages and this varied greatly across participants, ranging from 11% to 98%. Not one of the thirty participants spent the entire night sleeping on their left side.

Anxiety About Your Sleeping Position

According to another small study the majority (82.4%) of expecting mothers spend some time sleeping on their backs during pregnancy. Sleeping in a particular position seems like a simple thing to do and in practice, it isn’t that easy. You spend a lot of time in bed and you move around during sleep. Because you are asleep you are not consciously awake and aware of your position.

Many expecting mothers have woken up to find themselves lying on their back which immediately sets off concern that they have done something wrong. Questions can easily lead to anxiety. Have I been lying on my back all night? Is my baby getting enough oxygen? Is my baby at a higher risk for stillbirth? Anxiety is so common during pregnancy and while it is easier said than done, please do not panic if you wake up on your back.

In all of the research available on this subject, there is no evidence to give specific guidelines on what amount of time spent on your back increases your risk. There is evidence that very few expecting mothers are spending no time sleeping in a supine position. This is true even among those who had healthy babies. Sleep is so important to your overall health and the health of your baby. Losing sleep over stress about the position you are sleeping in does not do you, or your baby, any favors. 

Sleep Habits

You most likely sleep in the position you do out of habit. If you start training yourself to sleep on your side early in your pregnancy you can make it a habit for later in your pregnancy. The position is less important early in your pregnancy and becomes more of an issue as your belly grows and more weight can be put on your vena cava. It may not come easily at first, but with practice, you can change your habit around the position you sleep in.

How to Get and Stay in the Optimal Position

In pregnancy, you want to stack as many odds in your favor for a healthy baby. Let’s focus on what you can control to sleep on your side and minimize the pressure being put on your vena cava for maximum blood flow.

Start Sleeping on Your Left Side

You can start the night sleeping on your left side. This will at least guarantee some time in this position, even if you move while you are sleeping.

Optimize Your Sleeping Environment

Depending on your sleep environment laying on your left side may present some challenges. Think about the obstacles to laying on your left side and make changes to make that the more preferable side. 


You could have more exposure to light if you face a window or a bright alarm clock on your left side. The easiest fix for this is a sleep mask that blocks out light. Blackout curtains can help adjust the light coming from outside. Even if you have blackout curtains, you may need to adjust them to minimize light coming in from the top of the sides. Make adjustments to your alarm clock or devices that give off light. If you cannot decrease the brightness of an alarm clock face it away from you. You can place your phone face down on your nightstand. If you have other devices charging put a piece of electrical tape over any LED lights or change their placement.


If you have a partner who snores you may naturally face away from them when you sleep. If flipping over and facing them bothers you consider switching sides of the bed so you can lay on left and not be bothered as much by their snoring.

Getting Comfortable

If sleeping on your side is not your go-to position you may want to use some pillows to make this more comfortable. This is an area where pillows designed for pregnancy can really come in handy. You want support in some key areas, your back, your belly, and potentially between your knees. Supporting your bump will take some pressure off from the weight of your belly. Supporting your back can make you more comfortable. Putting a pillow between your knees can take some pressure off your hips and help align your spine. I like the pregnancy pillows from Boppy because they have different ones that can help give you the support you need to be comfortable while lying on your side, and to keep you on your side throughout the night.

Staying on Your Left Side

Falling asleep in a particular position is one thing, staying there for the entire night is another. Pillows can really help here. Boppy actually makes a specific pillow for sleeping on your side. It is basically two pillows connected with a panel of stretchy fabric to accommodate your growing bump. This way you have support on both your back and your belly, without a bulky pillow under your body. The magic of this pillow is that it is most comfortable on your side. If you fall asleep in the position and then move, you are not going to be as comfortable on your back and could be more likely to return to your side. You could also try putting a tennis ball or something in your bed behind your back so that if you do roll over it would remind you to go back to a side-lying position.

Remember, while the research may show that the left side is preferable, the goal is to avoid sleeping flat on your back. Even putting your body at an angle, even if you are not flat on one side will take some pressure off your vena cava. Having anxiety about your sleeping position is going to negatively impact your sleep. You can make adjustments to your sleep environment to promote side-lying positions.


Thank you to the amazing companies that have supported this episode.

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