【Ovulation 1905】

In 1905, Theodoor, Hendrik Van de Velde, a Dutch gynecologist, published a series of biphasic charts and noted that the length of elevated temperatures prior to menstruation was independent of the length of the menstrual cycle, thus demonstrating that the luteal phase is constant. He also made the connection that the upward shift was related to ovulation. By1926, he stated that it was the corpus luteum (the remains of the ovarian follicle after ovulation) that caused the upward shift in temperatures after ovulation. Van de Velde also observed the occurrence of mucus secretions and intermenstrual pain around the time of the thermal shift.

https://www.fertilityfriend.com/Faqs/A-brief-history-of-fertility-charting.html

 

It is not known exactly when it was first discovered that women have predictable periods of fertility and infertility. It is already clearly stated in the Talmud tractate Niddah, that a woman only becomes pregnant in specific periods in the month, which seemingly refers to ovulation. 

St. Augustine wrote about periodic abstinence to avoid pregnancy in the year 388 (the Manichaeans attempted to use this method to remain childfree, and Augustine condemned their use of periodic abstinence). One book states that periodic abstinence was recommended "by a few secular thinkers since the mid-nineteenth century," but the dominant force in the twentieth century popularization of fertility awareness-based methods was the Roman Catholic Church.

In 1905 Theodoor Hendrik van de Velde, a Dutch gynecologist, showed that women only ovulate once per menstrual cycle. 

In the 1920s, Kyusaku Ogino, a Japanese gynecologist, and Hermann Knaus, from Austria, independently discovered that ovulation occurs about fourteen days before the next menstrual period. Ogino used his discovery to develop a formula for use in aiding infertile women to time intercourse to achieve pregnancy.

In 1930, John Smulders, Roman Catholic physician from the Netherlands, used this discovery to create a method for avoiding pregnancy. Smulders published his work with the Dutch Roman Catholic medical association, and this was the first formalized system for periodic abstinence: the rhythm method.

 

https://en.wikipedia.org/wiki/Fertility_awareness