Give information about natural methods useful as contraceptives.

(N/A) Natural methods work on the principle of avoiding the chances of ovum and sperm meeting,which are as follows:
$(i)$ Periodic abstinence: In this method,couples avoid or abstain from coitus from day $10$ to $17$ of the menstrual cycle,when ovulation is expected. Since the chances of fertilization are very high during this period,it is called the fertile period. Therefore,abstaining from coitus during this period can prevent conception.
$(ii)$ Coitus interruptus: In this method,the male partner withdraws his penis from the vagina just before ejaculation to avoid insemination.
$(iii)$ Lactational amenorrhea: This method is based on the fact that ovulation and the menstrual cycle do not occur during the period of intense lactation following parturition. Therefore,as long as the mother breastfeeds the child fully,the chances of conception are almost nil. This method is effective only up to a maximum period of six months following parturition.
Since no medicines or devices are used in these methods,side effects are almost nil. However,the chances of failure for these methods are high.