Which hormone injection is administered by doctors to induce parturition?

Following features are seen during the dilation stage of parturition $EXCEPT$ . . . . . . .

$A$: Corticotrophin-releasing hormone is a part of the clock that establishes the timing of birth.
$R$: The signals for parturition originate from the fully developed foetus and placenta,which induce mild uterine contractions called the foetal ejection reflex.

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:

Which hormone is secreted at the time of parturition?

Which hormone helps in the process of parturition?