During birth, prostaglandins initiate the contraction in smooth muscles of uterine wall which causes labour pains. The pressure of fetus’s head against the cervix and send signals to make hypothalamus to trigger the release of oxytocin from posterior pituitary. Together, oxytocin (OT) and prostaglandins stimulate strong uterine muscle contraction forcing the fetus downwards and thereby expelling it out of uterus. Thus, to hasten the childbirth, it is advisable to administer the hormone that stimulates uterine smooth muscle contraction i.e. oxytocin. This makes option A correct. Thyroxine is a thyroid hormone which targets all tissues and stimulates metabolic rate, growth and development. Glucagon hormone from pancreas stimulates liver to break down glycogen into glucose and use of fat and protein as glucose source thereby increasing the blood glucose level. This makes options B and C incorrect as these hormones have no effect in parturition. Gonadotropic hormones (FSH and LH) stimulate ovary for egg production and release of sex hormones (estrogen and progesterone). This makes option D incorrect as estrogen and progesterone are maintained at minimal level to facilitate parturition. Correct answer is A.