Overview

Sleep is essential for your health, especially during pregnancy, but the changes that come with pregnancy can make quality rest more challenging. To add to the difficulty, certain sleep positions are often recommended—but how important are they? In this episode, we answer a listener’s question about whether she should be concerned about sleeping on her back. You’ll learn what the research says about sleep position during pregnancy, the potential risks and benefits of different positions, and practical tips to improve sleep without unnecessary stress.

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Hi Vanessa,

My sister recommended your podcast, and I’m so glad she did. I’ve learned so much already, and I really love how you break down all the information in such a clear and helpful way. Thank you!

I recently heard you mention in one of your episodes that lying on your back during pregnancy can decrease blood flow, which could reduce oxygen to both me and my baby. I have also heard that you are supposed to sleep on your side. I naturally sleep on my back, and I’m wondering if this is something I need to be concerned about. Does it really matter as long as you are sleeping okay? I want to make sure I’m doing what’s best for my baby, but I also don’t want to stress over something that isn’t actually a big deal.

I’m early on in my pregnancy, and if this is something I need to change, I want to correct it right away. Any info and advice is greatly appreciated.

Best,

Alex

Alex, thank you for your email. I love hearing that listeners find the podcast through recommendations and I’m so glad that both you and your sister find the podcast helpful.

Lying on Your Back

In a recent episode on Sorting Through Conflicting Advice on Pregnancy Workouts I discussed strength training and exercises that require you to lay on your back. As your uterus grows, it also puts more pressure on 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. When you lay on your back it puts additional pressure on this vein. The concern is that exercise positions where you lay on your back could decrease blood flow, ultimately reducing your oxygen and oxygen going to your baby. In regards to exercise, a systematic review concluded that supine (lying on your back) exercise is not associated with adverse pregnancy outcomes.

Sleeping on Your Back

There is a difference between lying on your back for a few minutes to complete an exercise and spending several hours on your back. Alex, you said that you naturally sleep on your back. There are some pros to this position. It is a good position for your spine. In the long term, sleeping on your back is also beneficial for your face. You may avoid wrinkles from sleeping with your face against a pillow, minimize acne and skin irritation, even blood circulation, and can reduce puffiness.

A downside of this position is that it can worsen sleep apnea or snoring, two conditions more common during pregnancy. Back sleeping also puts pressure on your vena cava, which can reduce oxygen to you and your baby. Pressure is also exerted on your intestines, making digestion less efficient. As a result, is it is generally recommended to avoid sleeping on your back in the second and third trimesters.

The Research on Sleep Position

The risk of pressure from your growing belly on the vena cava is greater as your pregnancy progresses and there is more weight in your uterus. Much of the research on sleep position during pregnancy looks at adverse outcomes that could result from reduced blood flow. The most concerning of those outcomes is stillbirth. A stillbirth is defined as the birth of a baby who dies in utero after 28 weeks. Before 28 weeks, it is considered a miscarriage. Stillbirth is a heartbreaking tragedy, and 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 to educate you.

Limitations of the Research

As we examine the research on sleep position and adverse outcomes we should acknowledge some common limitations of studies on this topic. First, they rely on self-reported data on sleeping positions. One study evaluated the accuracy of self-reported sleep position in late pregnancy. Participants spent three nights sleeping under observation and were asked to report their sleeping position., which was compared to video recordings to determine accuracy. On average, women accurately reported the time spent sleeping on their left side. However, some of the individual differences were as big as 3.5 hours. The downside of self-reported data is that it is not always accurate.

Another risk we see in research on this topic is the potential for recall bias. 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 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.

Lastly, it is difficult to establish a clear cause-and-effect relationship between solely sleeping on your back and stillbirth risk. Research suggests an association between sleep-disordered breathing and adverse outcomes such as hypertension and small-for-gestational-age infants, both of which are linked to an increased risk of stillbirth. Additionally, maternal obesity has been identified as a risk factor for stillbirth and is also associated with a higher likelihood of sleep-disordered breathing and sleep apnea, conditions that worsen when sleeping on the back. This creates a complex cycle, and nearly every study on this topic acknowledges the connection between the supine sleep position and sleep-disordered breathing, as sleeping on the back can exacerbate these issues.

Sleep Position and Adverse Pregnancy Outcomes

Now that you have some background on the limitations of studies on sleep position and adverse outcomes, let’s take a look at the research.

One study interviewed 155 women who had a stillbirth to determine whether snoring, sleep position, and other sleep practices were associated with the risk of stillbirth. Women who slept on their back or on their right side on the previous night were more likely to experience a stillbirth compared with women who slept on their left side. The absolute risk of 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 clinical trial specifically looked at the odds of stillbirth associated with self‐reported maternal going‐to‐sleep position on the night before 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 stillbirth were 2.3 times more likely to report going to sleep on their backs the night prior.

A large study including 8,706 women looked at sleep position and adverse pregnancy outcomes up to week 30 of pregnancy. Researchers found no association between sleep position the night or the week before the study visit and adverse pregnancy outcomes (stillbirth, small for gestational age babies, and gestational hypertensive disorders). Women with adverse outcomes also had higher BMIs, were more likely to smoke, have chronic hypertension, pre-gestational diabetes, and kidney disease. This study did collect reports of sleep position before the occurrence of the adverse outcome to eliminate the risk of recall bias.

Another study interviewed participants about their usual sleep position over the past month and compared the supine position to all other positions. 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.

The Ideal Sleeping Position

We know there are limitations in the research between sleeping position and stillbirth risk. Most of the studies are small but do show an increased risk of stillbirth with back sleeping. Although, it is unlikely that simply sleeping on your back is the sole cause of a stillbirth. We can conclude that sleeping on your back is not ideal during pregnancy. That leaves two options, sleeping on your stomach or your side.

If you usually sleep on your stomach, you may be okay continuing to sleep in this position through your first trimester. As your belly grows, you cannot maintain this position. This leaves us with side sleeping as the ideal sleeping position during pregnancy. If you have to pick a side, your left side is preferred. 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 for both you and your baby. Due to the location of your digestive organs, it may also improve digestion to sleep on your left side over your right.

Changing Your Sleeping Position is Easier Said Than Done

Sleeping in a particular position seems like a simple thing to do. However, it may not be so easy. In one study, participants were instructed to settle to sleep on their left side and, if they woke overnight, to settle back to sleep on their left. Video analysis indicated that participants spent around 60% of the night in this position. However, this was highly variable across participants, ranging from 11% to 98%. Not one of the thirty participants slept the entire night on their left side. Another study found 82.4% of expecting mothers spend some time sleeping on their backs during pregnancy.

In all of the research on this subject, there is no evidence to give specific guidelines on what amount of time spent on your back increases your risk. The goal is to maximize time on your side and not panic if you wake up on your back.

How to Get and Stay in the Optimal Position

There are some simple tips that can help you start sleeping on your side and remain in that position for most of the night. When you go to sleep start on your left side. This will at least guarantee some time in this position, even if you move during sleep. 79% of pregnant mothers report difficulty finding a comfortable position. As your body changes during pregnancy, the comfortable positions and how you support your body may need to evolve.

If you have trouble getting comfortable, pillows can make a significant difference. Pillows designed for pregnancy give you support in critical areas. 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 pressure off your hips and help align your spine. You may need to experiment with different pillow positions to find the most comfortable to fall and stay asleep.

If you are really concerned about sleeping on your side you could try putting a tennis ball or something in your bed behind your back so that if you do rollover it would remind you to go back to a side-lying position. However, you need to balance that with the disruption to your sleep if it is waking you up.

A Practical Approach

Your sleep position is largely a habit, and changing it takes time. Early in pregnancy, your sleeping position isn’t a major concern, but as your belly grows, it becomes more relevant. Alex, since you’re still early in your pregnancy, now is a great time to start training yourself to sleep on your side if you choose to. That said, sleep can already be challenging during pregnancy, so if you’re comfortable now, you don’t have to stress—adjustments can always be made later.

You asked if sleeping on your back is something to be concerned about. While it’s understandable to have concerns during pregnancy, it’s important to keep things in perspective. Rarely is there just one factor that causes an adverse outcome, so the goal is to stack the odds in your favor. Prioritizing side sleeping is ideal, but if that’s difficult and you’re otherwise sleeping well, it may not be a problem. The research suggests that the left side is preferable, but the key takeaway is to avoid lying flat on your back. Even a slight tilt can help relieve pressure on your vena cava.

There is overwhelming evidence that sleep is essential for you and your baby during pregnancy. However, many common pregnancy symptoms can make quality sleep more difficult, especially as your pregnancy progresses. While sleep position is one factor to consider, the last thing you want is anxiety over your position to negatively impact your sleep. The best approach is to aim for side sleeping when possible. If you wake up on your back, simply shift back to your side when you can. Using pillows can also make side sleeping more comfortable and help keep you in that position.

Ultimately, the goal is to get quality sleep while minimizing unnecessary risks. Do your best to sleep on your side when possible, but don’t panic if you wake up on your back. You can always bring up any questions with your doctor or midwife if you have additional concerns.

Additional Resources

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