How long it takes for a contraction to work is related to the sensitivity of the pregnant woman to the contraction, the condition of the cervix and other factors, and cannot be generalized. Contractins stimulate contraction of the smooth muscle of the uterus, causing the cervical opening to dilate. If the cervix is mature after 41 weeks of pregnancy but there are still no signs of labor, induction of labor can be performed with contractions. Normally, after the intravenous administration of indocin, the indocin reaches the body of the uterus with the blood circulation and binds to the indocin receptors in the myometrium, and regular uterine contractions occur. Usually, the contractions take effect within 30-60 minutes after the intravenous administration of indocin. However, some pregnant women may take up to 2 days for the contraction to take effect, and there are individual differences. In addition, pregnant women with scarred uterus and cephalopelvic disproportion should avoid the use of indocin to avoid the risk of pre-uterine rupture or even uterine rupture.