The causes of lumbago in the sixth month of pregnancy are the following: 1, the increase in weight during pregnancy can cause muscle tension causing muscle tension fasciitis, if accompanied by poor posture, such as sedentary, prolonged standing, such as bending over weight or bending over squatting work, long-term playing with cell phones, etc., can cause muscle tension aggravated. If encountered with strain and cold, the pain will be aggravated.2. Hormonal increase changes at this stage make ligaments relax and muscles easily damaged.3. After weight gain can stimulate the original lumbar spine pathology and produce lumbago, such as lumbar disc herniation and arthritis, which will gradually aggravate after weight gain.4. Low back pain may be combined with internal diseases, such as the presence of abdominal pain, nausea, or urinary urgency and pain, internal diseases or Urological diseases can also aggravate during pregnancy causing low back pain, and need to be checked clearly with symptomatic treatment.