NL 2005/01

Kyusaku Ogino (1882 -1975), cervical pessaries, Pearl Index

Dear friends of the Museum of Contraception and Abortion,

Who on earth was ’Ogino’, whose name has been associated with that of Austria’s Hermann Knaus? As is well known we owe to both of them the first correct calculation of fertile and infertile days in the female cycle, in itself a very unreliable method of contraception.

Working at the same time but independently, both Kyusaku Ogino (1882-1975) in Japan and Hermann Knaus (1892-1970) in Austria tried to find out whether or not there are fertile and infertile days and if so when they would be. Thanks to German catholic (!) missionary Hubert Reinirkens, Ogino was able to study the scientific views of eminent German medical researchers Ruge, Fränkel, Schröder, etc. These tried to calculate the fertile days by counting from the first day of bleeding but Ogino reversed the method of calculation and counted backwards. He supported his theory by histological examination of the ovaries of 65 women with very constant cycles. In 1923 Ogino published a draft in “Hokuetsu Medical Journal“.

Knaus presented his findings on womens’ fertile and infertile days at a gynecologists’ conference in 1929 in the German town of Leipzig.

Ogino’s and Knaus’ conclusions differ very little:


1st fertile day = shortest period minus 18 days

last fertile day = longest period minus 11 days


1st fertile day = shortest period minus 17 days

last fertile day = longest period minus 13 days

The first day of bleeding is understood as the first day of the female period.

In 1951 their method was recommended by Pope Pius XII in a speech given to members of the Catholic Italian Midwifes’ Association as the only acceptable and applicable method of contraception. Because of this and its high rate of unintended pregnancies it is nicknamed Catholics’ Roulette or Roman Roulette.


Especially frightening at the beginning of the 20th century were cervical pessaries, precursors of today’s coils. A small solid or open work disc some 20 mm in diameter, made from gold or some other material carried at its centre a small stick about 60 mm long which ended in two prongs resembling the letter “Y“. You might see some similarity with a golden cufflink or a mushroom. One idea behind these stem pessaries was to prevent the nidation of a fertilised egg in the uterus, the other was to shield the opening of the uterus against intruding sperm. Neither of these ideas worked, as sperm easily passes such an ineffective barrier and stems inserted into the uterus could induce severe irritation and infection – sometimes even perforation.

It was a technical challenge to find out how to insert these cervical pessaries with their two prongs. We discovered the simple but very smart answer in Megan Hick’s and Linda Adair’s leaflet “Taking Precautions: The Story of Contraception“ (1995). A piece of wax held the two prongs together while the pessary was being inserted and when the woman’s body heat melted the wax the prongs came apart and held the device in place.


The safety of contraceptive methods is indicated by the Pearl Index, which represents the number of failures (ie, unintended pregnancies) per 100 woman-years of exposure. The smaller this figure the better, although in fact this index gives a perfect use value instead of measuring typical use. That means it focusses on the effectiveness of a method instead of its usabilty.

A good example which demonstrates this important difference is the condom. In theory 5 percent of women experience an unintended pregnancy during their first year of using condoms, but in real life it is 21 percent. For periodic abstinence using methods of self-observation you see a perfect use index of 1 to 9 percent, but in real life 25 percent of users become pregnant unintentionally in their first year. The longer a couple uses a method the fewer unintended pregnancies occur because of more experience.

More about this topic can be read in: Contraceptive Technology by Robert A. Hatcher et al., Ardent Media, New York, 1998 (ISBN 0-9664902-0-7)


With a number of interesting new objects having already been donated, we are still happy to get more objects for the planned Museum of Contraception and Abortion, such as films, posters, leaflets, books, documents, statistics, devices and instruments used for contraception, for pregnancy-testing and for abortion - from past and present times, from locally and elsewhere.

You can also support us by sponsoring the purchase of objects, which otherwise we would not be able to finance.