Billings ovulation method

[3] It does not rely on the presence of ovulation, but identifies patterns of potential and obvious infertility within the cycle.

[1] A World Health Organization study found that 15% is caused by a conscious departure from method rules.

[1] In the days leading up to ovulation the cervix responds to oestrogen by producing mucus capable of sustaining sperm survival.

[6] The first recorded observations of the relationship between cervical mucus and survival of spermatozoa come from the mid-19th century.

During the course of his studies, he noticed that cervical mucus changed in a predictable pattern through the course of a woman's cycle.