It is generally safe and recommended for pregnant women to sleep on their sides, especially during the second and third trimesters. Sleeping on your left side can improve blood flow to the placenta and help prevent issues like swelling and back pain. However, sleeping on your right side is also acceptable. Sleeping on your back should be avoided as it may lead to decreased blood flow to the uterus and potentially increase the risk of stillbirth. If you find it uncomfortable to sleep solely on one side, using a pregnancy pillow or placing a pillow between your legs can provide additional support and comfort. As always, consult with your healthcare provider for personalized advice based on your specific circumstances.