Low back pain at 39 weeks of pregnancy may be caused by the following reasons: 1, the pregnant woman’s body hormones will change significantly in late pregnancy, resulting in pelvic ligament relaxation, which can adapt to the needs of future delivery, thus triggering the symptoms of low back pain in pregnant women; 2, the fetus is larger in late pregnancy, and the amniotic fluid in the pregnant woman’s body is also more, thus increasing the burden on the front of the pregnant woman’s lumbar spine, and the pregnant woman wants to maintain balance when standing, and needs to keep The lumbar back muscles continue to contract for a longer period of time, which can easily lead to lumbar fatigue and symptoms of lumbar pain; 3, pregnant women in late pregnancy due to mobility, exercise greatly reduced, long-term lying or sitting, which can easily cause lumbar pain; 4, the fetus in late pregnancy needs sufficient calcium to promote fetal bone development, if the intake of calcium is insufficient, it is easy to cause bone softening, which causes lumbar pain.