A Pound of Flesh or Just Proxy? Using Twin Differences to Estimate the Effect of Birth Weight on Life Chances

39 Pages Posted: 25 Aug 2003 Last revised: 4 Nov 2010

See all articles by Dalton Conley

Dalton Conley

New York University (NYU) - Department of Sociology; National Bureau of Economic Research (NBER)

Kate Strully

New York University (NYU) - Department of Sociology

Neil G. Bennett

CUNY Institute for Demographic Research; National Center for Childhood Poverty; National Bureau of Economic Research (NBER)

Date Written: August 2003

Abstract

Recent research into the implications of low birth weight may be plagued by unobserved variable bias. It is unclear whether the later-life consequences found to be associated with low birth weight are a true effect of poundage' at birth, or whether this association results from underlying factors related to birth weight such as genetics, gestational age, pregnancy-related behavior, or prenatal environment. In this study, we employ twin comparisons to rule out such unobserved factors and to isolate more precise effects of birth weight on infant mortality. Using data from the 1995-1997 Matched Multiple Birth Database and deducing zygosity based on the sex ratio of twin births, we examine the effects of birth weight for both fraternal and identical twins on both neonatal and post-neonatal mortality. Results suggest that in the neonatal period, low birth weight may partially be acting as a proxy for underlying genetic conditions, but in the post-neonatal period birth weight per se increases the risk of mortality. Thus, it appears that after an initial weeding-out' period in which the more severe ailments associated with genetics may be behind birth weight effects, poundage' itself has a significant impact on life chances net of genes and other pregnancy-specific health or social conditions.

Suggested Citation

Conley, Dalton and Strully, Kate and Bennett, Neil G., A Pound of Flesh or Just Proxy? Using Twin Differences to Estimate the Effect of Birth Weight on Life Chances (August 2003). NBER Working Paper No. w9901. Available at SSRN: https://ssrn.com/abstract=435463

Dalton Conley (Contact Author)

New York University (NYU) - Department of Sociology ( email )

New York, NY 10012
United States

National Bureau of Economic Research (NBER)

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

Kate Strully

New York University (NYU) - Department of Sociology

New York, NY 10012
United States

Neil G. Bennett

CUNY Institute for Demographic Research ( email )

Box D-901
One Bernard Baruch Way
New York, NY 10010
United States
6466606779 (Phone)

National Center for Childhood Poverty

The Joseph L. Mailman School of Public Health
Columbia University 154 Haven Ave.
New York, NY 10032
United States

National Bureau of Economic Research (NBER)

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

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