Season and Rate of Conception

Abstract

THE many difficulties of studying the effect of season upon birth-rate (or conception-rate) have been listed in Huntington's recent book “Season of Birth”. Factors such as birth control, a popular season for marriages, the return of males at holiday seasons, etc., all tend to obscure the actual relationship. Because conception—but not the number of young resulting from it—can be influenced in these ways, it seemed wise to find the seasonal effect by studying the ratio of multiple-conceptions to single-conceptions. (It is assumed that the seasonal factors affecting single-conceptions act in the same way, though to a greater extent, in affecting multiple-conceptions.) Suitable data are difficult to find ; the best I have been able to obtain are those from medical officers of health in the large cities, and the accompanying table summarizes those very kindly extracted for me by the Medical Officer of Health for Liverpool. They cover the two years 1935–1937. (To medical officers of health, births must be notified within thirty-six hours ; the Registrar-General's figures are not so reliable, as births may be notified up to forty-two days.)