What is foetal ejection reflex ? Explain how it leads to parturition ?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$ :

Assertion $A$ : Breast-feeding during initial period of infant growth is recommended by doctors for bringing a healthy baby.

Reason $R$ : Colostrum contains several antibodies absolutely essential to develop resistance for the new born baby.

In the light of the above statements, choose the most appropriate answer from the options given below:

$A$ : Synthesis of milk is stimulated by rise in the level of oxytocin.
$R$ : Oxytocin is released from the adenohypophysis under influence of hypothalamus.

What is meant by parturition ? Describe changes occurring in uterus during this period.

Signals for parturition originate from