NEW SEASONAL DISTRIBUTION OF BIRTHS IN NEW SOUTH WALES

Abstract

Since 1972 most births in New South Wales have been occurring in March rather than September (Table 1). The change began quite abruptly in 1972. Annual total births declined in 1966 increased between 1967 and 71 and declined again between 1972 and 76. The new seasonal distribution is not attributed to declining numbers because in the US seasonal distribution is not affected by rise and fall of annual birth rate. Nevertheless the change in New South Wales is a real one considering the precedent set by Puerto Rico. In both New South Wales and Puerto Rico the seasonal peak of births had moved from spring to autumn. Cowgill observed that Puerto Rico had shifted from a European-type distribution to that seen in the US and that during the 50s cultural attitudes had become Americanized; there is no evidence of such in New South Wales. Parker suggested that the change in seasonal pattern in South Wales may be partly attributed to maternal hyperthermia; however hyperthermia cannot account for changes in the pattern since 1971 as the climate has not noticeably changed. Cowgill in a later work made an association between the selenium status of soils in each state of the US and human fertility as measured by age-specific birth rates among whites. This raises the question of whether selenium is now entering the food chain in both Puerto Rico and New South Wales according to a changed seasonal pattern.