There is no best position for a woman to sleep in the second trimester of pregnancy, but it is generally primarily a side-lying position and is not recommended for the supine position. Women are generally not recommended to adopt the supine position in late pregnancy due to the larger fetus and larger uterus. This is because lying on the back tends to compress the inferior vena cava, which will have an impact on the return of blood to the pregnant woman, affecting the cardiac output. Reduced cardiac output can easily lead to postural hypotension, affecting the blood supply to the placenta, and may also lead to contractions, and may even have an adverse effect on the fetus. In the second trimester of pregnancy is generally mainly side lying position, for example, you can take the left side lying position, this sleeping position can help to reduce the uterus on the iliac artery and the aorta of the pressure, is conducive to the blood supply of the placenta. The left lateral position also helps to reduce the pressure of the uterus on the inferior vena cava, avoiding the hypotension syndrome caused by the supine position. However, long-term left-side lying position may have certain discomfort, so you can also be appropriate to change to the right side of the lying position, you can sleep on the left side of the lying position and the right side of the lying position alternately. In addition, women must rest more in the late stages of pregnancy, not to strain, but also to go to the hospital regularly for maternity checkups. Also pay attention to observe the physical condition, if there are signs of labor, to go to the hospital in time to wait for delivery.