Women are being advised to sleep on their side in the last three months of pregnancy, women in their third trimester are encouraged not to sleep on their backs. When they sleep on their back, the chances of the heavy uterus can reduce blood flow to the uterus and fetus, which can result in a stillbirth. Also, women are encouraged to sleep on their left side, as this is considered the best choice because the uterus naturally alternates to the right during pregnancy and left-sided lying will bring it more to the center and improve blood flow.
To help her sleep, a pillow can be placed between her legs or a long body pillow to support the back are often helpful. When a pillow is placed direct at her back and front, it helps support her body, resulting in a more comfortable position for sleep.
The major reason why she is having lightheadedness and dizziness when she lies on her back is that the weight of her uterus can compress a major blood vessel, called the vena cava, this then disrupts blood flow to the baby, leaving her nauseated, dizzy, and short of breath.
