Table 3.

Generalized additive model based on O₃ and demographic variables associated with birth weight (N = 407)^a.

Variables	Estimate	Standard	t/F	p-values
		error	value
Age (yrs)	11.228	6.067	1.851	0.065
Age at menarche (yrs)	−24.567	18.443	−1.332	0.184
Maternal education background	−4.689	22.678	−0.207	0.836
Menstrual status	−50.411	47.252	−1.067	0.287
Gestation	14.523	72.715	0.2	0.842
Parity	−42.01	80.012	−0.525	0.600
Gestational age (weeks)	101.398	19.55	5.187	< 0.001
Paternal smoking	21.169	49.692	0.426	0.670
Paternal alcohol consumption	9.772	51.018	0.192	0.848
Fetal gender	−92.465	36.628	−2.524	0.012
s(O3)			0.393	0.628
s(BMI)			4.039	0.002

^a O₃ and BMI are included as smooth terms, the edf values of them are 1.533 and 3.765, and the ref.df values of them are 1.925 and 4.645.