Doctors generally recommend sleeping on your side during pregnancy, especially as time goes on. Sleeping on your left side is often referred to as the “ideal” scenario during pregnancy because it allows for optimal blood flow from the inferior vena cava (IVC), a large vein that runs parallel to your spine on the right side and carries blood to your heart and, in turn, to your baby. However, experts generally agree that it is safe to sleep on the right side for short intervals.

Sleeping on your back or stomach after a certain point in your pregnancy is not recommended. Back sleeping during the second and third trimesters of pregnancy can compress blood vessels supplying the uterus and potentially harm the fetus or the mother. Stomach sleeping is also considered safe during early pregnancy, but it eventually becomes impossible, usually some time during the second trimester.

If you are having trouble sleeping on your side, try using pillows to prop your upper body at a 45-degree angle or elevating the head of your bed a couple of inches with books or blocks. It is important to note that a study funded by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) found that sleeping on the back or side through the 30th week of pregnancy does not appear to increase the risk of stillbirth, reduced size at birth, or high blood pressure disorders of pregnancy.