The 31 weeks of pregnancy belongs to the late stage of pregnancy, from time to time there is water flow may be premature rupture of fetal membranes, increased vaginal discharge or leakage of urine. 1. Premature rupture of membranes: vaginal water in 31 weeks of pregnancy may be premature rupture of membranes, if the breach is small, a small amount of intermittent water. 2. Increased vaginal discharge: Late pregnancy resistance is lower, easy to combine with bacterial infection, resulting in vaginitis, there will also be watery discharge. 3. Leakage of urine: in late pregnancy, due to the enlargement of the uterus, the pelvic floor tissues as well as the bladder will have obvious symptoms of compression, and there may be mild leakage of urine, which is also manifested as a small amount of water flow. When there is a small amount of water flow in the 31st week of pregnancy, you need to go to the hospital to find out the cause and actively deal with it.