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RESEARCH AND PRACTICE: Quanhe Yang, Sander Greenland, and W. Dana Flanders Associations of Maternal Age- and Parity-Related Factors With Trends in Low-Birthweight Rates: United States, 1980 Through 2000 Am J Public Health 2006; 96: 856-861 [Abstract] [Full text] [PDF]

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This could be due to increasing testostrone: The Secular Trend

James M. Howard   (5 June 2006)

This could be due to increasing testostrone: The Secular Trend 5 June 2006
James M. Howard, Biologist independent Send letter to journal: Re: This could be due to increasing testostrone: The Secular Trend jmhoward{at}anthropogeny.com James M. Howard	It is my hypothesis that the "secular trend," the increase in size and earlier puberty of children, is caused by an increase in the percentage of women of higher testosterone over time within the population. It is also my hypothesis that low birth weight is due to increased maternal testosterone (http://www.anthropogeny.com/Increasing%20Low%20Birth%20Weight%20in%20America.htm ). Black women produce more testosterone than white women. It is known that increased testosterone in women reduces fertility. I suggest the findings of Yang, et al., may be explained by the foregoing. That is, I suggest that low birth weight is increasing because maternal testosterone is increasing, and the attribution of later parity may also be due to the reduced fertility in women of higher testosterone.