. 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 6.

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

Prenatal risk factor	OLS	IV (2SLS)

	Birth Weight (grams)	Birth Weight (grams)

Cigarettes	−28.411^***	−55.434
	(5.239) [1792]	(73.937) [1792] {0.712}

Cigarettes among smokers	−29.551^***	−93.318^**
Cigarettes among smokers	(6.963) [441]	(50.100) [441] {0.161}

BMI	9.657^**	−111.637^*
	(4.773) [1791]	(58.860) [1791] {0.016}

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 < 0.05,

^***

p < 0.01