Table 3. Univariate linear regression analysis on the relationship of variables related to mean BW.

Variables	Estimate	SE	t value	Pr (> |t|)	Adjusted R2
Preterm births, %	−0.04	0.00	−12.21	< 0.001	0.88
LBWIs, %	−0.05	0.00	−14.51	< 0.001	0.90
Multiple births, %	−0.06	0.01	−10.36	< 0.001	0.82
Average maternal age, yr	−0.04	0.00	−14.68	< 0.001	0.90
Advanced maternal age, %	−0.01	0.00	−8.20	< 0.001	0.74

BW = birth weight, SE = standard error, LBWIs = low birth weight infants.