Final answer:
During the third trimester, a pregnant patient should be positioned on her left side, known as the left lateral recumbent position, to alleviate pressure on the inferior vena cava and to relieve back pain and circulatory issues.
Step-by-step explanation:
When transporting a pregnant patient in her third trimester, it is recommended to position her on her left side with the right knee and hip bent up toward the chest. This position is known as the left lateral recumbent position and is advised because it minimizes pressure on the inferior vena cava, which is a large vein that carries blood from the lower part of the body to the heart. During the third trimester, the uterus expands significantly, potentially compressing this vein when the woman lies on her back, a condition known as supine hypotensive syndrome. This positioning also alleviates back pain and can help with circulation issues that could arise from the fetus placing pressure on the blood vessels that return blood to the heart.
The third trimester is characterized by rapid growth and development of the fetus, often resulting in increased discomfort for the mother. During this period, the fetus can grow to weigh between 6 ½ to 8 ½ pounds and measure about 19-20 inches long, creating significant changes in maternal anatomy and weight distribution that contribute to symptoms such as back pain, varicose veins, and more frequent urination due to pressure on the bladder.