Describe the stages during three trimesters of pregnancy. Explain the process of parturition. Add a note on lactation.

Explanation

Pregnancy: The condition of carrying an embryo in the uterus means pregnancy of gestation. In human beings, gestation period is about 280 days.

Parturition:
(i) Parturition means act of expelling the full term baby out of mother's uterus after completion of gestation period.
(ii) Foetus secretes the hormone ACTH from its primary.
(iii) ACTH releases corticosteroids from its adrenal gland.
(iv) These foetal hormones enter maternal circulation by diffusion across placenta. These hormones decreases progesterone secretion of mother and increase in prostaglandin secretion. Oxytocin is secreted from mother's pituitary due to reduced progesterone levels.
(v) Oxytocin stimulates uterine contractions while the prostaglandins increase the force of contraction.
(vi) Baby is expelled out of the uterus.
(vii) Parturition is also called labour which has three stages, viz.,dilation or first stage, expulsion or second stage and placental or third stage.

(viii) Surgery or Cesarean section is performed in difficult situations of parturition when body is not normally delivered.
Lactation:
(i) Lactation is the process of production of milk through mammary glands. Lactation occurs after parturition.
(iii) The first milk secreted by mother is called colostrum which contains several antibodies.