A good night’s rest is important, but sometimes it can seem impossible. Sleep is even harder for pregnant women who have been told that sleeping on their back could suddenly harm or “cut off circulation” to a growing baby. The idea is understandably terrifying, and many women have lost sleep and endured discomfort while trying to avoid this supposedly deadly sleeping position.

If you’ve been keeping yourself up at night with the fear of waking up on your back, you can rest assured that this danger is a complete and total myth. While there is some truth that sleeping on your back can cause discomfort later in pregnancy, any danger to the baby is profoundly overstated.

Supine hypotensive syndrome is to blame

To many, it might seem strange that such a common sleeping position is rumored to be so dangerous to fetal health. The primary cause for this alarming myth is something called supine hypotensive syndrome. It is a physiologic occurrence that is related to the late third trimester of pregnancy.

During the later stages of pregnancy, the enlarging uterus becomes an abdominal organ and it naturally lists to the right. Its new position is often upon the same area as the inferior vena cava, one of the largest veins in the body. This vein drains blood from the legs and pelvis back up into the right atrium of the heart.

Late in pregnancy, every woman will notice some slight dizziness or lightheadedness if she lays on her back too long. This is due to the uterus applying pressure to the inferior vena cava. When this happens, the mom’s cardiac output drops somewhat and the blood flow to the mother’s brain is mildly decreased, leading to the feelings of dizziness or lightheadedness.

Change positions if youre uncomfortable

While supine hypotensive syndrome can sound alarming, resolving the issue is so simple that it’s often done instinctively. When a pregnant women has symptoms of dizziness, nausea, or faintness, then she will naturally change position, just as anyone would. Simply rolling to the side, sitting, or propping yourself up in a chair will increase the blood return to your heart, your cardiac output and the blood flow to your brain, thus resolving the symptoms.

The fear that these symptoms will suddenly deal lethal damage to the fetus is overtly wrong. These symptoms will be noticeable by the mom-to-be long before the baby experiences any complications. The baby’s circulation isn’t impaired, and fetal hemoglobin is much more effective at storing oxygen that the mother’s hemoglobin, so the baby is safe.

In addition, this syndrome is only likely to occur in the late stages of pregnancy when the uterus is significantly enlarged. There’s no need for any concern during the early months. If you’re approaching your late third trimester and worries about your position are keeping you up, just remember to move if you feel discomfort, much like you would normally.

Always speak with your doctor if you have any questions or concerns. No pregnancy is perfect, but I hope your pregnancy is the very best it can be.

If you’re interested in learning more about my practice, you can read more here. If you would like to make an appointment with me, you can contact Austin Perinatal Associates here.

Be safe, be well and have fun!

David L. Berry, M.D.

Founder and Staff Physician

Austin Perinatal Associates