In the first three months of pregnancy, due to some reasons such as stagnation of qi and dampness, the flow of qi and blood is not smooth, and pregnant women often appear drowsy, tired and other uncomfortable conditions. The choice of sleeping position in the first trimester should be based on comfort, and attention should be paid to avoid inattentive pressure on the fetus. And 18 weeks is the middle of pregnancy, the uterus has not reached large enough, you can sleep in a lateral position, preferably on the left side, to reduce the pressure of the enlarged pregnant uterus on the aorta and skeletal artery of pregnant women.