One of the first questions you may ask when you get pregnant (opens in new tab) is how should you sleep during pregnancy? You may have been told it’s essential to lie on your side during pregnancy, and even warned you could be harming your baby if you lie on your back.
Here, we take a look at the science behind the headlines, find out how to get the best night’s sleep for you and your baby, and ask whether products such as pregnancy pillows can help.
How does your sleeping position affect your baby?
There have been several studies suggesting a link between lying supine (on your back) in later pregnancy (in the third trimester, ie. from week 28) and late stillbirth.
One study (opens in new tab) in New Zealand, published in 2017, for example, concluded that sleeping on your back in the third trimester was associated with an increased risk of stillbirth. It led to a public health campaign telling women that if they avoided sleeping on their backs in late pregnancy (opens in new tab) they could reduce late stillbirth by approximately 9%.
An analysis of all the studies worldwide on maternal sleep and stillbirth, published in The Lancet (opens in new tab) in 2019, reached the conclusion that there was a connection between sleeping on your back in the third trimester and stillbirth, adding that, "This finding could reduce late stillbirth by 5.8% if every pregnant woman ≥ 28 weeks' gestation settled to sleep on her side."
These findings might seem highly alarming. According to Dr. Kellie Stecher, an obstetrician-gynecologist, and author of "Delivering (opens in new tab)," there’s no need to panic, however, as your body will naturally adapt to the correct position. "Your body typically will find ways to tell you not to lay in a position that is harmful to you or the baby," Kellie told Live Science.
In any event, she said, "The studies we have are underpowered and not randomized."
This view is supported by a paper published in Obstetrics and Gynecology (opens in new tab) in 2019 that cast doubt on the reliability of the data in previous studies. This substantial study, involving 8,706 women (between 22 and 30 weeks pregnant, so earlier on in pregnancy than the previous studies), included a cohort of women who wore a device to record their sleeping position so the study did not rely entirely on the participants' own accounts of how they slept. This study found no connection between sleeping position and stillbirth under 30 weeks, although it didn't cover the final 10 to 11 weeks of pregnancy.
In an editorial published alongside the study, Dr. Nathan Fox, associate clinical professor in obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai in New York City, noted that not only did previous studies involve small numbers of participants but, equally significantly, the women in all of those studies had self-reported their sleeping positions. It was possible that they had either misremembered or overemphasized their sleeping position as they believed it may have been the cause of the death.
How does your sleeping position affect your own health?
To be on the safe side, you’ll probably want to avoid sleeping on your back, particularly as you head into that third trimester, but as Kellie says, this will probably happen naturally. She says that the main reason to sleep on your back as your pregnancy progresses is for your own health and comfort.
"As you progress through pregnancy," she says, "the fetus is going to grow and the baby and uterus are becoming heavier. By about 20 weeks, in the second trimester, the weight of the uterus can cause you to have symptoms if laying on your back. The reason for this is the weight is pushing down on the vena cava, the big blood vessel returning blood to your heart. You will have symptoms when this is affecting you. Some women will feel nauseated, sweaty, hot and dizzy.
"Some women will also have increased acid reflux, making being on your back sub-optimal as well. Due to body composition changes, others will even have sleep apnea in pregnancy, especially third trimester. This is exacerbated by being on your back. It's important for you to find positions that are comfortable for you."
Should you change your sleeping position in each trimester?
As your baby gets bigger, you’ll find sleeping on your back becomes less and less comfortable, but you’ll probably find that your body adapts to the discomfort automatically.
There’s no need to worry if you find yourself rolling on to your side from time to time, according to Kellie. "This will happen to all of us. At some point in your pregnancy, you aren't going to feel well being on your back."
Should you sleep on your left side during pregnancy?
You may have read that you should sleep on your left rather than your right side. From the point of view of your baby’s safety, this advice has now been shown to be unnecessary - the analysis (opens in new tab) in the Lancet studies (see above) concluded that left and right-side sleeping were equally safe.
According to Kellie, "Either side is totally fine. Your liver is on the right side. Sometimes people will just have more discomfort because of this organ being on the right if they sleep on the right. There is no better side for baby."
Do pregnancy pillows help and what do they do?
Pregnancy pillows are shaped in a U, C or V shape, and are designed to help you to get comfortable as your baby bump grows, although many expectant mothers just use a regular pillow to get comfy.
"Pillows are great," Kellie told Live Science. "I find that placing a pillow under a growing baby bump can take pressure off of the ligaments on the side of the uterus. Also, placing a pillow between your knees and in the small of your back can help with the hip, knee, and back pain.
"Pillows will help with joint pain as well," she adds. "As the baby bump gets bigger there is more tension on your ligaments. Your joints become more sore as you go through pregnancy. Often people will have more pubic bone pain, hip pain, IT band pain, and sciatica. Pillows carefully placed can help take pressure off of some of these pain points."
What else will helps with sleeping when pregnant?
Above all, try to relax. "Just be easy on yourself," says Kellie. "It's OK if you wake up on your back. It's OK if you wake up on your stomach. Just find a way to be comfortable and get the sleep that you need."