The most common disease that causes more serious back pain after eight months of pregnancy is lumbar disc herniation, which is due to the fact that when pregnancy reaches its end, as the uterus grows, the fetus grows, and the amount of amniotic fluid increases, it makes the weight of the abdomen increase gradually, which will lead to lumbar disc herniation. The reason for this is that when pregnancy reaches its end, as the uterus grows, the fetus grows, and the amount of amniotic fluid increases, the weight of the abdomen increases, leading to the formation of lumbar disc herniation, and once the lumbar disc herniation is formed, it will lead to significant lumbar pain. 2. The reasoning is basically the same, both due to vertebral instability and muscle damage after a significant increase in lumbar weight bearing.