Sex ratios at birth in Scandinavia over the past sixty years

Abstract

Background: The gender ratio at birth (M/F: male births divided by total births) is expected to approximate 0.515. This has shown to be declining in industrialised countries and to display a latitude gradient in Europe, with more males born in southern climates. Methods: Annual national data for Scandinavian countries for male and female live births were obtained from the World Health Organisation and analysed with contingency tables. Results: This study analysed 18,250,193 live births. A significant decreasing trend in M/F was noted in all countries except Norway, and overall. There was no latitude gradient. M/F was less than 0.515 for almost all countries, with a resultant male deficit of 19,517 live births. Conclusions: M/F is decreasing in Scandinavia and M/F overall is <0.515. The interaction of several poorly comprehended factors is likely.