List various natural methods of birth control.

Explanation

Natural method of birth control is used to prevent meeting of egg with sperm.
These methods include Rhythm method (safe period), coitus interruptus, continuous abstinence and lactational amenorrhoea.
(i)Rhythm method: In menstrual cycle, the ovulation occurs at about the 14th day and ovum survives for about two days, where in the female reproductive tract, the sperms remain alive for about 72 hrs. If the coitus takes place avoiding these time, the fertilization may not take place.
(ii) Continuous abstinence: It is the simplest and most reliable method to avoid pregnancy. In this, it is better not to have coitus for a defined period that facilitates conception.
(iii)Coitus interruptus: It is the oldest family planning method, in which the male partner withdraws his penis before ejaculation, preventing the deposition of semen into the vagina.
(iv)Lactational amenorrhoea: After parturition, the menstrual cycle resume as early as 6-8 weeks. But during breast feeding, the menstrual cycle is delayed for about six months due to lactational amenorrhoea. During breastfeeding period, the sucking by the baby stimulates the pituitary to secrete more prolactin hormone in order to increase milk production. This increased concentration of prolactin in the blood suppress the release of Gonad Stimulating Hormone from hypothalamus, which in turn prevents the gonadotropin secretion from the pituitary, resulting in the prevention of menstrual cycle.