Sleeping on the left side during pregnancy is favorable to the fetus. With the increasing size of the uterus in late pregnancy, the uterus appears to varying degrees of rightward rotation, the ligaments around the uterus, the ligament, the tethered membrane is also in a state of tension, which contains blood vessels are also subjected to varying degrees of tension, which reduces the uterine blood supply, while the left lateral position can reduce the uterus rightward rotation, alleviate the uterine blood supply is insufficient, the growth and development of the fetus and the pregnant woman are favorable. If you keep sleeping on the left side at night, you may be more tired and exhausted, you can alternate between left and right positions; however, you should avoid prone position and supine position, prone position can compress the enlarged uterus, while in supine position, the enlarged uterus can compress the abdominal aorta, and supine hypotension can occur.