Table 2

Results of the OLS Regressions Explaining the Child’s Birth Weight in ALSPAC

	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
#Cigarettes smoked per day	–14.8**	–12.7**	–13.4**	–13.7**
#Cigarettes smoked per day	(1.3)	(1.3)	(1.7)	(1.7)
#Cigarettes smoked per day (adjusted)					–12.0**	–8.3**	–9.4**	–9.5**
#Cigarettes smoked per day (adjusted)					(1.3)	(1.5)	(1.8)	(1.8)
Birth weight PGS (child)			108.2**	104.6**			118.5**	112.8**
Birth weight PGS (child)			(7.0)	(7.4)			(10.0)	(12.0)
#Cig. smoked per day × Birth weight PGS				2.2
#Cig. smoked per day × Birth weight PGS				(1.5)
#Cig. smoked per day (adj.) × Birth weight PGS								1.3
#Cig. smoked per day (adj.) × Birth weight PGS								(1.6)
Control variables	No	Yes	Yes	Yes	No	Yes	Yes	Yes
R-squared	0.019	0.059	0.101	0.101	0.021	0.069	0.128	0.128
N	7,598	7,598	5,006	5,006	3,784	3,784	2,408	2,408

Notes: Coefficients are displayed with robust standard errors in parentheses; Columns 1–4 use the self-reported measure for smoking, and Columns 5–8 use the self-reported measure for smoking corrected using cotinine levels. PGS, polygenic score. All regressions correct for genetic relatedness among the mothers using the first four principal components of the genetic relationship matrix. +p < 0.1, *p < 0.05, **p < 0.01.