Effect of the Lebanese civil war on sex ratio.

Sex ratio is a subject of scientific interest but little is known about the factors that affect the sex ratio of humans. The aim of this study was to assess the effect of the Lebanese civil war on sex ratio. Data on all live births delivered at a large university hospital for the years 1977-2005 were used in this study. Study periods were defined as wartime (1977-1992) and post-war (1993-2005). The sex ratio in the study time period was calculated as the male proportion, i.e. males/males + females in live-born infants. Sex ratio during the war was compared with that of the post-war period. The sex ratio was similar in the war and post-war period (0.515 versus 0.513; OR = 1.007; 95% CI 0.98-1.04). The annual variation in the sex ratio during the study period did not show any significant change in any of the years. In conclusion, the Lebanese civil war did not cause a detectable change in sex ratio at birth. Factors that might have affected the sex ratio include the nature of the study population (civilians), the variable intensity of war in different periods, and the effect of stress and environmental toxins.