Margaret A.WinkerMD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Senior EditorIndividualAuthor
To the Editor: Dr Davis and colleagues1 noted that the proportion of male births in several countries had declined over varying periods in the past 5 decades and proposed that the sex ratio should be used as a sentinel health indicator to monitor possible effects of drugs and occupational and environmental exposures.
We analyzed Australian data on the proportion of male births since 1921 using data on national birth registrations published by the Australian Bureau of Statistics.2 We used linear regression to examine trends in annual averages for the 5-year periods 1921-1925 and 1991-1995 and annual data for the period between 1970 and 1996. There were 253834 registered live births in 1996, almost double the annual number in the early 1920s.
Lancaster PAL, Day PL. Declines in Population Sex Ratios at Birth. JAMA. 1998;280(13):1139-1141. doi:10-1001/pubs.JAMA-ISSN-0098-7484-280-13-jbk1007