Explain the three natural methods of birth control and underline the principle behind each method.

Explanation

(i) Periodic abstinence. Couples are advised to abstain from coitus during 10-17 days of menstrual cycle because ovulation occurs during this period.
(ii) Coitus interruptus. Semen is not inseminated inside vagina, because of withdrawal of penis before ejaculation.
(iii) Lactational amenorrhoea: No menstrual cycle/no ovulation, during intense lactation.