Declining trends of male proportion at birth in Europe

Declining trends in male proportion at birth observed in several Western co untries might reflect widespread exposure to pollutants capable of interfer ing with human reproduction. In this study, the authors describe male live birth proportion trends in 23 European countries from 1950 to 1996 (total o f 305 million live births). Overall, there was a significant linearly decre asing trend of 10 fewer males per 100,000 births each year, resulting in a loss of 73,462 boys during a 47-yr period. The proportion of male births du ring the first 3 yr of the study period was higher than in the last 3 yr in 18 countries (i.e., 78%). Decreasing trends, which varied in slope and sha pe, were observed in 11 countries; no significant trend was found in 8 coun tries, and male birth proportion increased in 4 countries. The results of t his study confirmed that the proportion of male births is declining in Euro pe, and differences exist by region and country. Social and cultural aggreg ations of countries with decreasing trends suggest that sociodemographic ch aracteristics might be more likely to explain trends than environmental exp osures to chemicals. Investigators should evaluate this hypothesis to asses s the usefulness of male birth proportion as a sentinel event.