In general, the pregnant woman may start to have effective contractions and abdominal pain within 24-48 hours after the placement of the water bag. As labor progresses, the pain will continue to increase and the fetus will gradually deliver on its own, but this may vary depending on the mother’s condition. If the mother and child have reached the indications for induction of labor but still have not initiated effective contractions, and if the cervical examination is not yet mature, and if there are no contraindications to induction of labor with a water bladder, the water bladder can be used to induce labor. The water bladder is an elastic plastic bladder, which is placed at the endocervix of the woman and swollen by injecting saline into the bladder to increase its volume to induce dilation of the cervical opening and contraction of the uterus, which in turn has an induction of labor effect, usually within 24-48 hours of placement. The following situations may occur after the placement of water bladder to induce labor: 1. If the pregnant woman has vaginal bleeding, abdominal tension or rising trend of uterine fundus after the placement of water bladder, placental abruption should be considered, and it is recommended to take out the water bladder, closely observe the situation of mother and child, and give timely treatment; 2. If vaginal fluid appears after the balloon is placed, be alert to premature rupture of membranes and remove the balloon as soon as it is diagnosed to avoid infection.