Some of that advice overload you've been getting has probably included cautionary tales about never sleeping on your stomach or back for fear of injuring your baby. The truth is this: If a certain sleep position is bad for your baby or you, you'll know it because it will be so uncomfortable that your body will naturally shift.
Where do these cautions come from? Never sleeping on your stomach makes a certain amount of sense -- after all there's a baby between you and the bed, and sleeping on your stomach may make you feel like you've rolled over onto a football. That position is probably more uncomfortable for you than it is for your baby, however, and the uterus is designed to protect your baby from harm.
As for never sleeping on your back, that rule stems from the fact that you have major blood vessels that lie to the right of your spine. Sleeping on your back causes the weight of the uterus to press down on them and decrease blood circulation. When you compress one of these veins, known as the vena cava, less blood flow is returned to your heart. That can make your blood pressure drop enough to make you feel sweaty, dizzy, or even nauseous. But don't worry. Your body naturally protects you and your baby in this situation: By the time your uterus is heavy enough to compress the vein, you'll be so uncomfortable lying on your back that your body will flip over, even if you're asleep. So go ahead and sleep any way you like. If it makes you feel better, though, you can use pillows to wedge yourself onto your side; that will become your comfiest and most practical sleep position by the end of your pregnancy.
Originally published in You & Your Baby: Pregnancy.
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