These methods are less efficient than artificial methods.
They are based on sexual abstinence during the fertile days of each cycle. Their efficiency is close to 94% (depending on the method chosen). They are generally not very reliable.
There are three ordinary methods to find the “risk days”:
- Calendar or Knaus-Ogino method: it consists of being sexually abstinent during and after ovulation (between the 8th and 18th day of the cycle). This is the least reliable of natural contraception methods.
- Basal temperature method: the temperature is taken each morning on waking up and before doing anything. Any sexual relation should be avoided between the last day of the periods and three days after the increase in temperature.
- Cervical mucus or Billings method: at the time of ovulation, the cervical mucus goes from a thick consistency and not very abundant to a more profuse, fluid and transparent secretion. Sexual relations are allowed on alternate days from the last day of periods until the detection in the increase of cervical mucus secretion.
- Sympto-thermal method: it combines the temperature and cervical mucus methods.