A particularly sore lower back is not necessarily a sign of pregnancy, because when you are clinically newly pregnant, the hormone level in your body has not yet reached a certain level, and the uterus is not rapidly increasing in size, so there is no involvement pain and no corresponding other symptoms. If the lumbar region is particularly sore, it is necessary to exclude the possibility of other diseases, such as soreness caused by lumbar muscle strain or inflammatory reaction of the sacral ligament due to pelvic inflammation, which can cause pain in the lumbosacral region, all of which can cause the symptoms of a particularly sore lumbar region. In addition, after pregnancy, as the number of days of pregnancy increases, if the uterus is in retroflexion and retroversion, the symptoms of lumbar pain may appear only after 45-50 days of pregnancy.