They include i. Basal body temperature (BPT) ii. Cervical mucus method iii. Symptothermic method. These methods involve recognition of some physiological signs and symptoms associated with ovulation.
1. Basal body temperature method (BBT):
Due to the production of estrogen, there is an increase of 0.3 to 0.5°C in BBT at the time of ovulation The period during which there is an increase in BBT can be avoided for intercourse, since it is not safe.
2 Cervical mucus method:
It is also known as “Billing’s method” or “ovulation method”. At the time of ovulation cervical mucus becomes watery clear (like raw egg white), smooth, slippery and profuse. This can be recognized and intercourse is avoided during this period.
3. Symptothermic method
It combines BBT, cervical mucus and rhythm method. The principle is, if one sign fails, the other sign may help.
It is generally believed that lactation prolongs postpartum amenorrhea and it can provide protection against pregnancy. But once menstruation returns, lactation does not protect against pregnancy.
Birth control vaccine:
A vaccine has been prepared from beta sub- unit of human chorionic gonadotropin (HCG). Immunization with this vaccine blocks the continuation of pregnancy. Immunity can be boosted by a second injection.