Hormone responsible for causing labour pain is:

The correct answer is Option (2) → Oxytocin

Parturition (childbirth) is brought about by strong contractions of the uterus, which are felt as labour pain. The signals for it come from the fully developed foetus and the placenta. They cause mild uterine contractions called the foetal ejection reflex. This makes the maternal pituitary release oxytocin. Oxytocin causes stronger contractions of the uterine muscle, which in turn cause more oxytocin to be released. So the contractions grow stronger and stronger until the baby is born.

(1) Testosterone — Incorrect. It is a male hormone made by the Leydig cells of the testis.

(2) Oxytocin — Correct. It causes the strong uterine contractions of labour.

(3) Vasopressin — Incorrect. It is also released by the pituitary, but it controls water reabsorption in the kidney.

(4) Progesterone — Incorrect. Progesterone keeps up the pregnancy. It does not cause labour.

NCERT Extract:
Parturition and Lactation –