| Declines in Sex Ratio at Birth and Fetal Deaths in Japan, and in U.S. Whites but Not African Americans Devra Lee Davis,1 Pamela Webster,1 Hillary Stainthorpe,2 Janice Chilton,3 Lovell Jones,3 and Rikuo Doi4 1Center for Environmental Oncology, University of Pittsburgh Cancer Institute and Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; 2Feinberg School of Medicine, Northwestern University, Evanston, Illinois, USA; 3Center for Research on Minority Health, University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA; 4Yokohama City University, School of Medicine, Yokohama, Japan Abstract
Background: The expected ratio of male to female births is generally believed to be 1.05, also described as the male proportion of 0.515. Objectives: We describe trends in sex ratio at birth and in fetal deaths in the United States, in African Americans and in whites, and in Japan, two industrial countries with well-characterized health data infrastructures, and we speculate about possible explanations. Methods: Public health records from national statistical agencies were assembled to create information on sex ratio at birth and in fetal deaths in the United States (1970–2002) and Japan (1970–1999) , using SPSS. Results: Sex ratio at birth has declined significantly in Japan and in U.S. whites, but not for African Americans, for whom sex ratio remains significantly lower than that of whites. The male proportion of fetal death has increased overall in Japan and in the United States. Conclusions: Sex ratio declines are equivalent to a shift from male to female births of 135,000 white males in the United States and 127,000 males in Japan. Known and hypothesized risk factors for reduced sex ratio at birth and in fetal deaths cannot account fully for recent trends or racial or national differences. Whether avoidable environmental or other factors—such as widespread exposure to metalloestrogens or other known or suspected endocrine-disrupting materials, changes in parental age, obesity, assisted reproduction, or nutrition—may account for some of these patterns is a matter that merits serious concern. Key words: African Americans, environment, fetal deaths, Japan, race, sex ratio, trends. Environ Health Perspect 115: 941–946 (2007) . doi:10.1289/ehp.9540 available via http://dx.doi.org/ [Online 9 April 2007]
Address correspondence to D.L. Davis, 5150 Centre Ave., Suite 432, Pittsburgh, PA 15232 USA. Telephone: (412) 623-1172. Fax: (412) 623-1382. E-mail: davisdl@upmc.edu E. Reitano, J. Kuo, and Y.-Y. Han provided research assistance in final preparation of this manuscript. A. Ilaqua assisted in the retrieval of data sources, as did J. Lee and T. Suzuki. Constructive comments also were received from F. Mudagno, R. Ness, E. Talbott, and K. Burns. Funding was provided by The Heinz Endowments, the University of Pittsburgh Cancer Institute, DSF Charitable Trust, the U.S. Centers for Disease Control and Prevention, and the W. Alton Jones Foundation. The authors declare they have no competing financial interests. Received 21 July 2006 ; accepted 1 March 2007.
The full version of this article is available for free in HTML or PDF formats. |
