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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: Biodemography Soc Biol. 2013;59(1):4–36. doi: 10.1080/19485565.2013.774615

Table 7.

Effects of Risk Factors on Birth Weight under OLS and IV (2SLS) Models with Genetic Instruments in ALSPAC

Prenatal risk factor OLS IV (2SLS)
Number of cigarettes (first
trimester)		 −14.035***
(1.280)
[6947]		 −28.270
(23.554)
[6947]
{ 0.542}
Number of
cigarettes among
(first trimester)
smokers		 −3.422
(2.201)
[1341]		 −42.571
(25.323)
[1341]
{0.087}
Any alcohol use
(firsttrimester)		 32.877*
(14.769)
[6683]		 355.315
(332.896)
[6683]
{0.327}
Number of units of alcohol
(first trimester)		 1.285
(1.572)
[6697]		 −187.651
(301.782)
[6697]
{0.272}
BMI 19.991***
(1.969)
[6566]		 −112.017
(196.182)
[6566]
{0.363}

Note: The table reports the coefficients from the regressions of birth weight on prenatal risk factors; standard errors are in parentheses; sample sizes are in brackets; p values for significance of the difference between OLS and 2SLS estimates are in curly brackets. A separate regression is estimated for prenatal factor.

*

p < 0.1,

***

p < 0.01