Because an increase in oxytocin level increases the contractions
Oxytocin can be defined as a hormone that usually acts on organs of the body which includes the uterus and breast. They can also act as a chemical messenger in the brain by controlling some important aspect of reproductive system such as lactation and childbirth. However, the positive feedback mechanism of oxytocin is that an increase in release of oxytocin will stimulate more contractions.