Kyusaku Ogino

Kyusaku Ogino (25 March 1882 - 1 January 1975) was a Japanese doctor specializing in obstetrics and gynecology.

His natural father's last name was Nakamura, but Kyusaku was adopted by the Ogino family in 1901.

Ogino studied infertility and developed a method to estimate the fertile period of the menstrual cycle based on the length of a woman's past cycles. This knowledge could be used by couples seeking pregnancy to time intercourse so as to maximize the chances of conception.

Hermann Knaus in Austria later modified Ogino's method so that it could be used for contraception (the Rhythm Method). Ogino opposed the use of his method as a contraceptive method. He argue that a failure rate is too high and to promote his method as a method of contraception despite the availability other effective contraceptive methods would result in many abortions from unwanted pregnancies. Despite this, the Rhythm Method of contraception is ironically referred to as the Ogino Method in Japan.