According to the NCERT text, Natural methods work on the principle of avoiding chances of ovum and sperms meeting. Periodic abstinence is explicitly mentioned as 'one such method in which the couples avoid or abstain from coitus from day 10 to 17 of the menstrual cycle' . Intra Uterine Devices (IUDs) and Hormonal pills (oral contraceptives) are artificial methods involving devices or chemical preparations , .