Allan B B, Brant R, Seidel J E, Jarrell J F
Department of Obstetrics and Gynecology, University of Calgary, Alta.
CMAJ. 1997 Jan 1;156(1):37-41.
To examine the trends in the proportion of annual live births that were male in Canada and to compare the trends with those in the United States.
Analysis of census data.
Canada as a whole and 4 main regions (West, Ontario, Quebec and Atlantic).
All live births from 1930 to 1990.
Sex ratio (expressed as the proportion of total live births that were male [male proportion]) overall and by region.
The male proportion in Canada decreased significantly after 1970 (p < 0.001); this represented a cumulative loss of 2.2 male births per 1000 live births from 1970 to 1990. Although a decrease was observed in all four regions studied, only that in the Atlantic region was significant (p < 0.001), representing a cumulative loss of 5.6 male births per 1000 live births from 1970 to 1990. A significant decrease in the male proportion was also observed in the United States from 1970 to 1990 (p < 0.001), although to a lesser degree than that observed in Canada, and represented a cumulative loss of 1.0 male births per 1000 live births.
The decreased sex ratio in Canada adds to the growing debate over changes in biological markers and their potential causes. In addition, the study illustrates the potential use of the sex ratio as a widely available, unambiguous measure of the reproductive health of large populations.
研究加拿大年度活产男婴比例的变化趋势，并与美国的趋势进行比较。
人口普查数据分析。
加拿大全国以及4个主要地区（西部、安大略省、魁北克省和大西洋地区）。
1930年至1990年的所有活产儿。
总体及各地区的性别比（以活产男婴占总活产儿的比例[男性比例]表示）。
1970年后加拿大的男性比例显著下降（p<0.001）；这意味着1970年至1990年每1000例活产儿中男性减少了2.2例。尽管在所研究的所有四个地区均观察到下降，但只有大西洋地区的下降具有统计学意义（p<0.001），即1970年至1990年每1000例活产儿中男性减少了5.6例。1970年至1990年美国的男性比例也显著下降（p<0.001），尽管降幅小于加拿大，每1000例活产儿中男性减少了1.0例。
加拿大性别比的下降加剧了关于生物标志物变化及其潜在原因的争论。此外，该研究表明性别比有可能作为一种广泛可用、明确的衡量大群体生殖健康的指标。
