Which one of the given statements defines the term 'parturition'?

The correct answer is Option (2) → The process of delivery of foetus

Option (1) The average duration of human pregnancy — Incorrect. That is the gestation period, about 9 months in humans.

Option (2) The process of delivery of foetus — Correct. At the end of pregnancy, vigorous contractions of the uterus expel the foetus; this is parturition, induced by a neuroendocrine mechanism with oxytocin.

Option (3) Production of milk by mammary glands — Incorrect. That is lactation. The mammary glands make milk towards the end of pregnancy to feed the new-born; it is not the act of birth.

Option (4) The milk produced during initial few days of lactation — Incorrect. That milk is colostrum, rich in antibodies (IgA) that protect the new-born. It is a kind of milk, not the act of birth.

NCERT Extract:
Parturition and Lactation – “The average duration of human pregnancy is about 9 months which is called the gestation period. Vigorous contraction of the uterus at the end of pregnancy causes expulsion/delivery of the foetus. This process of delivery of the foetus (childbirth) is called parturition. Parturition is induced by a complex neuroendocrine mechanism.”