Can You Prevent Pregnancy, Do Share These methods are much less reliable as a form of birth control than the traditional contraceptive methods. 1. Calendar / Rhythm Depends on calculation of Fertile and Non fertiledays. If you have a normal 28days cycle the fertile days falls between 11th to 18th day, avoid sexual intercourse during this time 2. Basal Body Temperature The core temperature or the BBT goes down by a little degree just before the ovulation & then rises after ovulation stays a littl