A small amount of water flowing at 39 weeks of pregnancy may be caused by premature rupture of fetal membranes, increased vaginal discharge, and urine leakage. 1. Premature rupture of membranes: when there is a small amount of vaginal fluid at 39 weeks of pregnancy, it may be rupture of membranes. There may be a small amount of intermittent vaginal fluid, or an increase in the amount of fluid after activity, which can be combined with clinical signs and ultrasound examination, and measurement of the pH (acidity and alkalinity) of vaginal fluid may assist in the diagnosis. 2. Increased vaginal discharge: vaginitis may occur in late pregnancy, resulting in increased vaginal discharge, which may be thin and watery, and amniotic sacs may be palpable on routine sterilized vaginal examination, and the pH of vaginal fluid is negative. 3. Leakage of urine: at 39 weeks of pregnancy, due to the fetal prelude into the pelvis, the pelvic floor tissues and bladder compression is obvious, there may be mild symptoms of leakage of urine, but also show a small amount of water flow. When 39 weeks pregnant with a small amount of water flow need to go to the hospital, has identified the cause, and actively deal with.