Perhaps only slightly improve the performance of muscles of the uterus. (health-and-parenting.com)
[17][18] Oxytocin contracts the smooth muscle of the uterus during birth and following delivery, called the postpartum period, while breastfeeding. (en.wikipedia.org)
It is safe, and it won't hurt the baby because he is protected by the amniotic sac and the strong muscles of the uterus. (babygaga.com)