Oxytocin can promote uterine contractions, how long it takes to work is related to the pregnant women’s individual physique and the route of injection, most of them can take effect within a short period of time. 1. Individual physique: pregnant women’s physique varies, so does the time for oxytocin to take effect, for pregnant women who are sensitive to oxytocin, it usually takes about 1 minute for oxytocin to enter the body to take effect and make the uterine contractions stronger. For pregnant women who are unresponsive to oxytocin, it may take 1-2 hours for it to take effect, or it may even have no effect. 2. Injection route: If oxytocin is injected directly into the uterine body or intravenously, it usually takes 1-2 minutes to take effect and cause uterine contractions. If oxytocin is injected intramuscularly, it needs to pass through the capillaries of the muscle to reach the uterus. Also, some of the drug may have been inactivated during diffusion into the bloodstream, reducing the effective blood concentration, and it may take 5-10 minutes or more for the drug to take effect. In addition, the pelvic size and fetal orientation should be evaluated by the doctor before oxytocin injection to avoid inappropriate use leading to obstructed labor or even uterine rupture. Excessive dosage of oxytocin may cause strong contractions or uncoordinated contractions, which may raise the blood pressure of the pregnant woman and cause emergency labor or prolonged labor, with adverse effects on the mother and fetus.