Economic conditions or other weighty reasons may put couples in a position in which they need to limit their offspring. Conversely, it is also true that there are a great number of women who desire children and who wish to know the most opportune time for a fertile intercourse. Since most women look to their family physician for guidance in this matter, we feel that an intimate acquaintance with this subject is desirable. Our practical experience in the field of natural conception control enables us to present data and corroborative proof showing that the Ogino-Knaus theory as represented is correct and practical for all normal, healthy and regularly menstruating women.
There were several difficulties in the path that prevented scientists from solving this problem during the last few centuries. Nature, so to speak, threw them off their track in their search for the solution by suggesting a similarity between menstruation
LATZ LJ, Reiner E. NATURAL CONCEPTION CONTROL. JAMA. 1935;105(16):1241-1246. doi:10.1001/jama.1935.02760420011003