Declining male births with increasing geographical latitude in Europe

Objective-Demographic studies in various industrialised countries have show n a decline in male births in the latter half of the 20th century from the expected ratio of 0.515 (males/total). This study analyses trends in this r atio over the period 1890 to 1995 in Malta, and also analyses this ratio fo r Western European countries for the period 1990-1995. Design-Births subdivided by sex were obtained from official Maltese publica tions. European countries were grouped according to geographical latitude b y banding countries into three groups: Northern Mediterranean, Central Euro pean and Scandinavian. Births by sex for these countries were also analysed for the period 1990-1995. Results-No decline in the ratio of male births to total births was noted in Malta over the period 1916-1995. However, the ratio was higher than expect ed (n=151 766, ratio=0.517(95% confidence intervals (95%CI): 0.514, 0.519). Moreover, during the period 1890-1899 (n=66 874), the ratio was 0.523 (95% CI: 0.519, 0.527), even higher than observed during the 20th century (chi( 2)=8.3, p=0.003). Analysis of European births showed a much higher ratio of male births in the south of Europe than in the north (chi(2)=87.2, p<0.000 1). Conclusions-The findings were unable to explain the higher incidence of mal e births in the south of Europe, but it is speculated that ambient temperat ures may not only affect fertility, but also influence sex ratios at birth.