The first thing to consider when it comes to back pain in the third trimester is the muscular soft tissue aspect that causes soreness, pain and discomfort in the lower back. This is because after any woman becomes pregnant, her weight will increase rapidly in a short period of time, resulting in an increased load on the lumbar spine. After the load on the lumbar spine increases, the corresponding soft tissue tension in the lumbar back increases, causing chronic muscle strain in the lumbar back, resulting in low back pain. Secondly, neurological factors should be considered. Because many female patients have slight herniated or bulging discs, which usually have no clinical symptoms, but after pregnancy because of weight gain, the original herniated or bulging discs will be further aggravated on top of the original, compressing the dural sac, posterior longitudinal ligament and nerve roots, leading to increased back pain. Therefore, the above two factors are the most common ones, both of which are caused by the increased load on the lumbar spine after weight gain, resulting in the aggravation of the corresponding symptoms in the muscles and soft tissues or nerves. What should I do if I have back pain in the third trimester of pregnancy? First, you should rest and try to avoid increasing the burden on the lumbar spine. Secondly, we should strengthen the functional exercise of the muscles of the lumbar back and both lower limbs. Third, physiotherapy can be performed when necessary, as medication should be avoided after pregnancy.