In the early and middle stages of pregnancy, when the uterus grows in the lower part of the pelvis and abdominal cavity, the pressure on the pregnant woman is relatively light, so any position can be taken to sleep at this time, without special requirements. In late pregnancy, due to physiological effects, the uterus will rotate to the right and compress the right inferior vena cava. If a pregnant woman lies in the right or flat position for a long time, it is easy to cause supine hypotension, and the right vascular compression will cause serious obstruction of reflux, which may even cause hydronephrosis or ureteral dilatation on the right side of the pregnant woman. It is recommended that pregnant women in late pregnancy try to take the left lateral position or more left lateral position, and try not to lie flat. Therefore, pregnant women can sleep on their right side after pregnancy.