Academic journal article Environmental Health Perspectives

Shift in the Sexes: Are Endocrine Disruptors Changing Birth Ratios?

Academic journal article Environmental Health Perspectives

Shift in the Sexes: Are Endocrine Disruptors Changing Birth Ratios?

Article excerpt

According to demographic data compiled by the United Nations, an average of 105 boys are born for every 100 girls. The male proportion of births, equal to 0.515, varies slightly between years and populations, but these factors do not fully explain consistently shifting ratios in several industrialized countries over recent decades. A new study examines birth and fetal death sex ratios in Japan and the United States and reveals significant male-to-female shifts in both nations [EHP 115:941-946; Davis et al.].

The research team calculated birth and fetal death sex ratios in Japan based on 1949-1999 data from the Japanese Vital Statistics Bureau. The proportion of male births varied yearly before 1970 but declined steadily since then, from 0.5172 to 0.5135. Between 1960 and 1999, the male proportion of fetal deaths increased from 56% to 67.7%. The male fetal death rate is approximately four times higher in Japan than in the United States.

For U.S. calculations, the researchers drew 1983-1995 fetal death data and 1970-2002 birth data from the National Center for Health Statistics. The proportion of male births dropped in the United States, from 0.5134 in 1970 to 0.5117 in 2002. There are significant racial differences, however: between 1970 and 2002 the proportion of non-Hispanic white male births fell from 0. …

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