Why Are You Supposed to Sleep on Your Left Side During Pregnancy?

Pregnancy is a time full of lifestyle changes and new adjustments. From the expected (no more smoking!) to the bizarre (no more hot dogs?), it can be hard to filter out the good advice from the bad. One tip you may have heard from friends, family, or your healthcare provider is that you should only sleep on your left side, but just how important is it to follow that advice, and what are the risks if you don't? Ultimately, it is good advice to sleep on your left side if you're able, but if you can't, don't sweat it.

Why sleeping on your back is a bad idea
Although sleeping on your back during early pregnancy isn't likely to cause problems, back-sleeping can be a huge pain in the butt (literally) during the late stages. The American Pregnancy Association warns that moms who sleep on their backs have a higher rate of discomforts like hemorrhoids, back pain, and stomach aches. As your belly grows, sleeping on your back also puts pressure on your aorta and vena cava, two important blood vessels that move blood to and from the placenta. As a result, sleeping on your back could reduce the amount of oxygen and nutrients that your baby receives.
 
Why your left side, not your right?
 
The vena cavae blood vessels (big veins that return blood to your heart from your abdomen) are located just to the right side of your body, so sleeping on your right side might be a bad idea. There's some evidence that, like sleeping on your back, right-side sleeping could put a lot of the baby's weight against your blood vessels. This might reduce the amount of blood pumping to and from your heart, which could have bad consequences for the baby.

What happens if you sleep in the "wrong" position?

 
Hopefully, nothing. We don't yet know exactly what might happen if you don't sleep on your left side during pregnancy, since it hasn't been studied very well. In theory, it seems like babies whose moms sleep in other positions might have a lower birth weight. One very unsettling study found that women who slept on their backs during pregnancy had well over twice the risk of giving birth to stillborn babies. Even though this study had some limitations and the findings weren't conclusive, it's still safest to try to sleep on your left side if you're able.

If you can't sleep on your left side...
 
Don't worry too much. Evidence of danger to your baby from other positions is very limited. For example, the most publicized study on the issue only looked at the outcomes of a fairly small number of women, and they relied on women's self-reporting, which isn't always reliable, especially after something as traumatic as a stillbirth. So, for now, there's not enough evidence to sweat it if you absolutely can't get comfortable on your left side. However, you may want to try adjusting your sleep position by experimenting with body pillows or raising the head of your bed to see if it helps. You might be able to get a restful night's sleep in the safest position possible, but, if the discomforts of pregnancy make it too difficult, there isn't a reason to worry.

Of course, as always, talk to your doctor or midwife about any concerns about your health that you may have during any stage of pregnancy. Your health care provider can offer reassurance or help provide personalized advice that can make it easier to sleep safely and comfortably while you await your baby's arrival.