A woman not using any other contraceptive method can avoid pregnancy by abstaining from coitus during 

Periodic abstinence is a natural birth control method in which the couples avoid or abstain from coitus from day 10 to 17 of the menstrual cycle when ovulation could be expected. As chances of fertilisation are very high during this period, it is called the fertile period. Therefore, by abstaining from coitus during this period, conception could be prevented.