Trends in the human sex odds at birth in Europe and the Chernobyl Nuclear Power Plant accident

To investigate trends in the sex odds before and after the Chernobyl accident, gender-specific annual birth statistics were obtained from the Czech Republic, Denmark, Finland, Germany, Hungary, Norway, Poland, and Sweden between 1982 and 1992. For parts of Germany, annual birth statistics and fallout measurements after Chernobyl are available at the district level. Trend models allowing for discontinuities of the male birth proportions are suggested. Superimposed on a downward trend in male proportions there was a jump in 1987 with a sex odds ratio of 1.0047 (95%-confidence interval: 1.0013-1.0081, p = 0.0061). A positive association of the male proportion in Germany between 1986 and 1991 with radioactive exposure at the district level is reflected by a sex odds ratio of 1.0145 per mSv/a (1.0021-1.0271, p = 0.0218). These findings suggest a possible long-term chronic influence of the Chernobyl Nuclear Power Plant accident on the human sex odds at birth in several European countries.