The ‘detective of the fertile days’

07/02/2017 - 13:16

The Museum for Contraception and Abortion (Vienna, Austria) published the book "Der Detektiv der fruchtbaren Tage" about the Austrian scientist Hermann Knaus. This publication has been supported by an ESC (grant P-2015-A-06).

Having the option of choosing from so many safe and effective contraceptives today, we owe our thanks to many Austrian scientists. An outstandingly important one was Hermann Knaus (1892-1970), the ‘detective of the fertile days’. In the late 1920’s, after years of testing, Knaus and the Japanese gynaecologist Ogino simultaneously discovered which days in women’s menstrual cycle are fertile and which are infertile and how these days could be calculated. This put an end to the conjectures by means of which the doctors over centuries sought to crack the secret of fertility. Until then, contraception came up to pure lottery. Thanks to Knaus, women/couples were finally able to break free from the constraints of constant childbearing imposed on mankind by nature: 15 pregnancies during a woman´s lifetime being ‘natural’ or ‘intended by nature’. Moreover, the ‘day counting’ according to Knaus proved equally successful in treatment of unintentionally childless marriages in respect to both, the natural and the in vitro fertilisation. The method also provided a scientific basis for determination of paternity and led to generation of major physiologic principles culminating in the development of the “Pill”. For his achievements, Knaus had been nominated for the Nobel Prize in 1936.

More information about the book and how to order (in German) on the website of the Museum.

Fact Sheet: Who was Hermann Knaus?

Knaus was born in 1892 in St. Veit an der Glan (Carinthia, Austria) into a wealthy merchant family. After his military service in WW1 and his medical studies in Graz, he spent a semester in Great Britain in 1924, in order to study experimental surgery on animal uterine muscles. In 1928, during a medical conference in Berlin, Knaus was able to observe vigorous contractions of human uterus under an X-ray screen at the University Women’s Hospital Berlin, whereas at another time the muscles appeared limp and slow. Instigated by these observations Knaus, then assistant doctor at the University Women’s Hospital in Graz, began to draw graphic records of the movements of human womb. He realised that even in humans the corpus luteum (placed in the ovary after ovulation) causes the uterine muscles relax and slacken, beginning some 12 days before the next menstruation.

In order to clearly identify the precise time of ovulation, Knaus asked his patients to keep accurate records of their menstrual periods. Using these he was able to deduce that ovulation and the start of luteal activity always start 14 days before the next menstruation with a maximal variation of 48 hours. This fact can be taken for granted, as the luteal formation and regression inside of the burst follicles proceed at very regular intervals, as long as no pregnancy occurs.

In 1929, Knaus presented his newest insights about the fertile and infertile days of the female cycle at the gynaecology congress in Leipzig. In 1934 he put out his menstruation calendar as a practical calculation tool.

In particular, we owe three major findings to Knaus:

  • The female egg’s ability to become fertilized lasts just a few hours.
  • The male sperm’s ability to fertilize is limited to a few days.
  • The time interval between the ovulation and subsequent menstruation remains constant.

It was already in 1923 when the Japanese gynaecologist Prof. Kyusaku Ogino (1882 -1975) had his preliminary paper published, presenting similar observations. At that time, however, no German or Anglo-American scientist could have possibly noticed a publication from the faraway Japan.

Professor Knaus acted as head of the large Women´s Hospital at the German University in Prague from 1934 to 1945 and from 1950 till 1960 he became department head at the Wien-Lainz Hospital. Apart from his scientific work, Knaus significantly contributed to his subject as gynaecologist, obstetrician, surgeon (specialising in cervical cancer), university teacher and trainer of junior medical staff. He died in Graz in 1970 and was buried in his home town St. Veit an der Glan. On his very deathbed, Knaus received pontifical blessings brought by a Vatican Nuncio.


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