Which layer of the uterus is responsible for parturition?

Which of these is not an important component of the initiation of parturition in humans?

What is parturition? Which hormones are involved in the induction of parturition?

Which gland in the female undergoes differentiation during pregnancy and lactation?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$ :
Assertion $A$ : Breast-feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.
Reason $R$ : Colostrum contains several antibodies absolutely essential to develop resistance in the newborn baby.
In the light of the above statements,choose the most appropriate answer from the options given below:

The contraction of the uterus at the time of childbirth is stimulated by $........$.