Is Canada's sex ratio in decline?

In this issue (see pages 37 to 41) Dr. Bruce B. Allan and associates report a small but statistically significant decrease--of about 0.2%--in the proportion of male live births in Canada over the period 1970-90. In this editorial, factors that have been reported in the literature to influence sex ratio are examined within a Canadian context. The authors suggest that although the reasons for the apparent decline in the sex ratio in Canada are unclear, the increasing use of ovulation induction may be a contributing factor. Data from the Nova Scotia Atlee Perinatal Database are discussed with a view to explaining the trend observed in Atlantic Canada, but no obvious explanation emerges. The authors argue that when the period of observation is extended no overall change in the sex ratio is apparent. This would suggest a tendency toward stabilization rather than decline.