<prompt> Which of the following Natural method of contraception is most effective?Calendar methodBilling methodSymptothermic methodBasal body temperature method  <response>: Ans. c Symptothermic method Ref. Parks textbook of PSM 22nd403, 404CONTRACEPTIVE METHODS SPACING : Barrier methods, -Intrauterine devices, -Hormonal, -Postconceptional, Miscellaneous Abstinence Coitus interruptus Safe periodRhythm methodCalendar methodOgino method Natural family planning- Basal body temperature- Cervical mucus Billings methodovulation method- Symptothermic combination of temperature, cervical mucus, and calendar technique TERMINAL: -Male sterilization and -Female sterilizationDrawbacks of the Calendar Method of Contraception If cycle is irregular, it is difficult to predict the safe period. It is possible only for use by educated and responsible couples with high motivation and cooperation. Compulsory abstinence of sexual intercourse for nearly 12 of every month is required programmed sex. It has high failure rate up to 10 per 100 woman years. It is applicable during the postnatal period. Ectopic pregnancies and embryonic abnormalities have been reported as result of safe period method use. 